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FRAUNHOFER-INSTITUT FÜR WERKSTOFF- UND STRAHLTECHNIK IWS

6th WORKSHOP »LITHIUM-SULFUR BATTERIES«

November 6 – 7, 2017 Fraunhofer IWS Dresden, Germany

CONFERENCE DOCUMENTS WORKSHOP „LITHIUM-SULFUR-BATTERIES VI“ NOVEMBER 6 - 7, 2017

Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS Winterbergstraße 28, 01277 Dresden

November 6, 2017

10:00 Registration

Session I Trends in material development Chair: Prof. Dr. Stefan Kaskel, Fraunhofer IWS, TU Dresden

11:00 Welcome and opening Prof. Dr. Eckhard Beyer Fraunhofer IWS, TU Dresden

11:15 Solvate ionic liquids for lithium‐sulfur batteries Prof. Masayoshi Watanabe, Yokohama National University, Japan

12:00 Importance of carbon materials in positive electrodes of the lithium-sulfur batteries Dr. Elena Karaseva, Ufa Institute of Chemistry of Russian Academy of Sciences, Russia

12:30 Chemical engineering science of lithium metal anode in lithium-sulfur batteries Prof. Qiang Zhang, Tsinghua University, China

13:00 Lunch break

Session II Lithium metal anodes Chair: Prof. Dr. Stefan Kaskel, Fraunhofer IWS, TU Dresden

14:15 Lithium/electrolyte interfaces Prof. Jürgen Janek, Justus-Liebig-Universität Gießen, Germany

14:45 Suitability of sulfide based solid state electrolytes for use in lithium metal secondary batteries Dr. Yuichi Aihara, Samsung R&D Institute Japan

15:15 Lithium metal anodes for lithium-sulfur batteries Stephen Lawes, OXIS Energy Limited, UK

15:45 Coffee break

16:15 Lithium-metal film deposition for Li-S-cells with high volumetric energy density Dr. Benjamin Schumm, Fraunhofer IWS

16:45 Handling and processing of metallic lithium in the production of next generation battery cells Anna Kollenda, Technische Universität München, Germany

17:15 Short poster introduction (Short presentation of some selected posters in preparation of the poster session)

17:45 Poster session and dinner at Fraunhofer IWS

WORKSHOP „LITHIUM-SULFUR-BATTERIES VI“ NOVEMBER 6 - 7, 2017

Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS Winterbergstraße 28, 01277 Dresden

November 7, 2017

Session III Cathode chemistry and new electrolytes Chair: Dr. Holger Althues, Fraunhofer IWS

09:00 Is lithium-sulfur ready for commercial uptake? Market demand and competition Gleb Ivanov, Sigma Lithium Ltd

09:30 Stabilizing sulfur carbon cathodes - a biotechnology approach Mark Griffiths, EndLiS Energy, USA

10:00 On the factors affecting the capacity depletion of lithium-sulfur batteries at the cycling and storage Dr. Elena Kuzmina, Ufa Institute of Chemistry of Russian Academy of Sciences, Russia

10:30 Coffee break

11:00 Impact of adapted nitrate-free electrolytes on pouch cell performance Dr. Susanne Dörfler, Fraunhofer IWS

11:30 Sparingly solvating electrolytes design for high energy density lithium-sulfur batteries Dr. Kevin R. Zavadil, Sandia National Laboratories, USA

12:00 Effects of Li-anion interactions on solubility of lithium polysulfides in ionic liquids Dr. Seiji Tsuzuki, National Institute of Advanced Industrial Science and Technology (AIST), Japan

12:30 Lunch break

13:45 Characterization of reaction intermediates in lithium-sulfur battery via operando transmittance UV/Vis spectroscopy Qi He, TU München, Germany

14:15 Operando characterization of a lithium-sulfur battery by coupling X-ray absorption tomography and X-ray diffraction Guillaume Tonin, CEA Grenoble, France

14:45 Thermal effects and diagnosis tools in multilayer cells for real applications Dr. Monica Marinescu, Imperial College, UK

15:15 Concluding remarks Prof. Dr. Stefan Kaskel, Fraunhofer IWS, TU Dresden

15:30 Tour through the labs of the Fraunhofer IWS (optional 1h)

With my registration I agree with the potential publication of photographs taken during the event and with the electronic storage of my address (incl. the use of my address for future invitations).

LECTURE

Solvate ionic liquids for lithium‐sulfur batteries

Masayoshi Watanabe

Department of Chemistry and Biotechnology, Yokohama National University 79‐5 Tokiwadai, Hodogaya‐ku, Yokohama 240‐8501, Japan

Innovation in the design of electrolyte materials is crucial for realizing next‐generation electrochemical energy storage devices such as Li–S batteries. The theoretical capacity of the S cathode is 10 times higher than that of conventional cathode materials used in current Li– ion batteries. However, Li–S batteries suffer from the dissolution of lithium polysulfides, which are formed by the redox reaction at the S cathode. Herein, we present simple solvate ionic liquids, glyme–Li salt molten complexes [1], as excellent electrolyte candidates because they greatly suppress the dissolution of lithium polysulfides [2]. Certain concentrated mixtures of salts and solvents are not simply "solutions" anymore, but they may be described as "solvate ionic liquids", in which the solvents strongly coordinate the cation and/or the anion of the salts to form stable “solvate ions”. All of the solvents interact with the cation and/or anion, so that the liquids can be classified into “solvate ionic liquids” [3, 4]. Equimolar molten mixtures of glymes (triglyme (G3) or tetraglyme (G4)) and lithium bis(trifluoromethane sulfonyl)amide (Li[TFSA]) are typical examples that we propose [1]. The equimolar complexes [Li(G3 or G4)][TFSA] are stable + ‐ liquids consisting of [Li(glyme)1] complex cation and [TFSA] anion, both of which are extremely low coordinating ions with low Lewis acidity and basicity, respectively [3]. The [Li(G3 or G4)][TFSA] molten complexes do not readily dissolve other ionic solutes due to the low coordinating nature of the cation and anion, which leads to the stable operation of the Li–S battery over more than 400 cycles with discharge capacities higher than 700 mAh g‐sulfur‐1 and with coulombic efficiencies higher than 98% throughout the cycles [2]. Furthermore, the addition of a nonflammable fluorinated solvent, which does not break the solvate structure of the glyme–Li salt molten complexes, greatly enhances the power density of the Li–S battery [2]. It is also interesting to note that the [Li(G3 or G4)][TFSA] molten complexes are compatible with Si and graphite anodes [5], which makes it possible to construct Si‐Li2S and graphite‐Li2S batteries [6] on the basis of the fabrication of high performance Li2S/C cathode [7]. This paper deals with fundamental properties of solvate ionic liquids, and how characteristics of the solvate ionic liquids can be utilized in advanced Li‐S batteries.

References: [1] K. Yoshida, M. Nakamura, Y. Kazue, N. Tachikawa, S. Tsuzuki, S. Seki, K. Dokko, M, Watanabe, J. Am. Chem. Soc. 2011, 133, 13121‐13129. [2] K. Dokko, N. Tachikawa, K. Yamauchi, M. Tsuchiya, A. Yamazaki, E. Takashima, J.‐W. Park, K. Ueno, S. Seki, N. Serizawa, M. Watanabe, J. Electrochem. Soc. 2013, 160, A1304‐A1310. [3] K. Ueno, K. Yoshida, N. Tachikawa, K. Dokko, M. Watanabe, J. Phys. Chem. B 2012, 116, 11323‐11331. [4] T. Mandai, K. Yoshida, K. Ueno, K. Dokko, M. Watanabe, Phys. Chem. Chem. Phys. 2014. 16, 8761‐8772. [5] H. Moon, R. Tatara, T. Mandai, K. Ueno, K. Yoshida, N. Tachikawa, T. Yasuda, K. Dokko, M. Watanabe, J. Phys. Chem. C 2014, 118, 20246‐20256. [6] Z. Li, S. Zhang, S. Terada, X. Ma, K. Ikeda, Y. Kamei, C. Zhang, K. Dokko, M. Watanabe, ACS Appl. Mater. Interfaces, 2016, 8, 16053‐16062. [7] Z. Li, S. Zhang, C. Zhang, K. Ueno, R. Tatara, K. Dokko, M. Watanabe, Nanoscale, 2015, 7, 14385‐14392. Importance of carbon materials into positive electrodes of the lithium-sulfur batteries

Vladimir Kolosnitsyn, Elena Karaseva, Elena Kuzmina

Ufa Institute of Chemistry of the Russian Academy of Sciences, Laboratory of Electrochemistry, Prospect Oktyabrya 71, Ufa, 450054, Russia

Lithium-sulfur batteries belong to the batteries with a liquid depolarizer, since during their charge and discharge the solid-phase substances (sulfur and lithium sulfide) are converted into compounds - lithium polysulfides (Li2Sn), which are highly soluble in electrolytes. Mechanisms of electrochemical processes occurring in lithium-sulfur and lithium-ion batteries are significantly different. The active materials of the positive electrode in charged (sulfur) and discharged (lithium sulfide) states are dielectrics and don’t have electrochemical activity in solid state. However, sulfur is soluble into electrolyte systems of the lithium-sulfur batteries, and lithium sulfide is able to dissolve in electrolytes as lithium polysulfides. These properties of active materials also allow to involve both elemental sulfur and lithium sulfide into electrochemical conversions. The electrochemical reduction of sulfur during discharge of the lithium-sulfur batteries includes several stages - dissolution of elemental sulfur, diffusion transfer to the surface of the carbon current collector, sorption on the surface of the carbon current collector, electrochemical reduction, desorption of the reduced products from the surface of the carbon current collector. Similar processes occur also when lithium- sulfur cells are charged. Electrochemical processes which occur in the lithium-sulfur cells during charge and discharge are heterogeneous and are carried out at the interface between ionic and electronic conductors. The ionic conductor is an electrolyte saturated with active materials (sulfur or lithium polysulfides), and the electronic conductor is various types of carbon materials (carbon black, carbon nanotubes, graphenes, etc.). The depth and speed of electrochemical reactions during charge and discharge of the lithium-sulfur batteries are determined by the properties of carbon materials, entering into the composition of the sulfur electrode and performing the functions of the current collectors. Carbon materials used into positive electrodes of the lithium-sulfur batteries should have:  high electronic conductivity;  high specific surface area;  good sorption properties towards sulfur and lithium polysulfides;  resistivity to passivation of the surface of carbon particles by solid products of electrochemical reactions (by sulfur and lithium sulfide);  ability to form into positive sulfur electrode a bulk carbon network with high electronic conductivity. The report summarizes the results of study the correlation between properties of carbon materials, entering into the composition of the sulfur electrode, and performance of the lithium-sulfur cells. It is shown that the most important factors affecting the depth of electrochemical transformations of sulfur and lithium polysulfides, cycling life of the lithium- sulfur cells are chemical and physical properties of carbon materials, their specific surface area, porous structure, continuity of the ionic and electronic conducting networks of the sulfur electrodes. This work was supported by RFBR, research project No.16-29-06190. Chemical Engineering Science of Li Metal Anode in Li-S Batteries

Xin-Bing Cheng, Rui Zhang, Chong Yan, Xue-Qiang Zhang, Qiang Zhang*

Department of Chemical Engineering, Tsinghua University, Beijing 100084, China

Li metal is considered as the “Holy Grail” of energy storage systems. The bright prospects give rise to worldwide interests in the metallic Li for the next generation energy storage systems, including highly considered rechargeable metallic Li-S batteries. However, the formation of Li dendrites induced by inhomogeneous distribution of current density on the Li metal anode and the concentration gradient of Li ions at the electrolyte/electrode interface is a crucial issue that hinders the practical demonstration of high-energy-density metallic Li batteries. In this talk, we will focus on the chemical engineering issue of Li metal anodes. Firstly, we will introduce the solid electrolyte interfaces on a working Li-S batteries. The composition and structure of solid electrolyte interfaces were modulated and implantable into other electrolyte system. Secondly, the nucleation of Li metal is probed. The nitrogen doped graphene was adopted as the Li plating matrix to regulate Li metal nucleation and suppress dendrite growth. Finally, we explained the efforts to regulate the Li metal deposition through ultralow local current density and the introduction of solid electrolyte. These results indicated that interfacial engineering of Li metal anode electrode can handle the intrinsic problems of Li metal anodes, thus shed a new light toward Li-S batteries with high energy density and long cycle life.

References: [1] X. B. Cheng, H. J. Peng, J. Q. Huang, F. Wei, Q. Zhang, Small 2014, 10, 4257 [2] X. B. Cheng, H. J. Peng, J. Q. Huang, R. Zhang, C. Z. Zhao, Q. Zhang, ACS Nano 2015, 9, 6373. [3] R. Zhang, X.B. Cheng, C.Z. Zhao, H.J. Peng, J.L. Shi, J.Q. Huang, J.F. Wang, F. Wei, Q. Zhang. Adv Mater 2016, 28, 2155. [4] X.B. Cheng, T.Z. Hou, R. Zhang, H.J. Peng, C.Z. Zhao, J.Q. Huang, Q. Zhang, Adv Mater 2016, 28, 2888. [5] X.Q. Zhang, X.B. Cheng, X. Chen, C. Yan, Q. Zhang, Adv Funct Mater 2017, 27, 1605989. [6] X.B. Cheng, R. Zhang , C.Z. Zhao, F. Wei, J. Zhang, Q. Zhang, Adv Sci 2016, 3, 1500213. [7] X.B. Cheng, C. Yan, J.Q. Huang, P. Li, L. Zhu, L.D. Zhao, Y.Y. Zhang, W.C. Zhu, S. Yang, Q. Zhang, Energy Storage Mater 2017, 6, 18. [8] C.Z. Zhao, X.B. Cheng, R. Zhang, H. Peng, J. Huang, R. Ran, Z. Huang, F. Wei, Q. Zhang, Energy Storage Mater 2016, 3, 77-84. [9] C. Yan, X.B. Cheng, C.Z. Zhao, J.Q. Huang, S.T. Yang, Q. Zhang, J Power Sources 2016, 327, 212. [10] X.B. Cheng, C. Yan, X. Chen, C. Guan, J. Huang, H. Peng, R. Zhang, S. Yang, Q. Zhang, Chem 2017, 2, 258. [11] X. Chen, T.Z. Hou, B. Li, L. Zhu, C. Yan, X.B. Cheng, H. Peng, J. Huang, Q. Zhang, Energy Storage Mater 2017, doi: 10.1016/j.ensm.2017.01.003. [12] R. Zhang, X.R. Chen, X. Chen, X.B. Cheng, X.Q> Zhang, C. Yan, Q. Zhang, Angew Chem Int Ed 2017, doi: 10.1002/anie.201702099.

Suitability of sulfide based solid state electrolytes for use in lithium metal secondary batteries

Yuichi Aihara, Satoshi Fujiki, Nobuyoshi Yashiro, Naoki Suzuki, Takanobu Yamada, and Tomoyuki Shiratsuchi, Ryo Omoda, Tomoyuki Tsujimura, Seitaro Ito, Taku Watanabe, Youngsin Park and Yunil Hwang

Samsung R&D Institute Japan, 2-1-11 Senba-nishi, Minoo-shi, Osaka 562-0036, Japan

Lithium metal secondary batteries had been studied during the 80s until a serious incident occurred in ‘89 and their use was subsequently limited to small applications involving very low current usage with a shallow load cycle (e.g., coin cells for memory back up). After the successful production of lithium ion batteries (LIBs), with their inherent safety and high energy density, most companies switched their R&D efforts to LIBs from the early 90s. Now, however, especially in the automotive field, the application of lithium metal batteries has again attracted attention due to expectation of their high energy density above current LIBs. But their safety must be guaranteed (i.e., no repetition of the ’89 incident). Many technical problems must be addressed before they can be adopted as practical large scale batteries (e.g., lithium dendrite formation, excess lithium and electrolyte for compensating the consumption during cycle). These problems are closely related to the side reactions between lithium and the electrolytes. Preventing the side reactions is the most important key [1-2]. We have found that sulfide based solid electrolytes show great promise for avoiding the above issues. Recently, we demonstrated the cycle durability of a (pellet size) solid state Li-S cell [3]. In this presentation, we demonstrate further capabilities of a solid-state system based on Li-NCA and Li-S cells in our prototype batteries. Since the charge/discharge efficiency is always >99.9%, we expect longer cycles than that in a general liquid system Also, the 0.5C cycle was performed with a high loading level above 5 mAhg-1 for the cathode (Fig. 1). These favorable characteristics result from the solid state nature. Our results establish that the solid state lithium metal secondary battery is a great next generation battery candidate.

Fig. 1 Charge-discharge curves of solid-state secondary battery based on sulfide electrolyte.

[1] K. M. Abraham, J. S. Foos, and J. L. Goldman: “Long Cycle-Life Secondary Lithium Cells Utilizing Tetrahydrofuran”, J. Electrochem. Soc., 1984, 131, 2197 – 2199. [2] S. Tobishima, M. Arakawa, T. Hirai and J. Yamaki: “Ethylene Carbonate/Ether Solvents for Electrolytes in Lithium Secondary Batteries”, J. Power Sources, 1987, 20, 293 – 297. [3] Y. Aihara, S. Ito, R. Omoda, T. Yamada, S. Fujiki, T. Watanabe, Y. Park and S. Doo: “The Electrochemical Characteristics and Applicability of an Amorphous Sulfide-Based Solid Ion Conductor for the Next-Generation Solid-State Lithium Secondary Batteries”, Front. Energy Res. 2016, 4:18. Lithium metal anodes for lithium-sulfur batteries

Stephen Lawes

OXIS Energy Limited, E1 Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB, UK

Lithium-sulfur batteries are the most promising candidates for next-generation energy storage. Their high energy density, low cost, and safe chemistry make Li-S batteries particularly suited for electric vehicles, grid storage, and aerospace applications. However, challenges still exist for the widespread commercialization of lithium-sulfur batteries. The main barrier to entry is cycle life; current Li-S batteries with high energy densities (>375 Wh/kg) can only achieve cycle lives of around 50 to 100 cycles. This is due to continuous side reactions at the lithium metal anode that consume the cell’s active materials and electrolyte.

A massive research effort is underway in both academia and industry to solve the problems of using lithium metal as an anode material. Longer cycle life has been achieved by creating protective coatings on lithium metal that can effectively withstand large volume changes and prevent continuous electrolyte depletion. These coatings also enable the use of lower electrolyte loadings and less excess lithium, which in turn leads to higher energy density.

At OXIS Energy, we are currently developing protective polymer and ceramic coatings on lithium metal anodes for rechargeable lithium-sulfur batteries. These mechanically robust and chemically stable passivation layers effectively prevent contact between lithium metal and electrolyte, leading to high cycling efficiency and improved cycle life. In this presentation, the strategies employed by OXIS Energy for using lithium metal anodes in commercial Li-S batteries will be presented. Lithium-metal film deposition for Li-S-cells with high volumetric energy density

Benjamin Schumma, Paul Härtela,b, Christine Wellera,b, Markus Piwkoa,b, Sebastian Tschöckea, Daniel Koebbela, Holger Althuesa, Stefan Kaskela,b aFraunhofer IWS, Winterbergstraße 28, 01277, Dresden, Germany bDresden University of Technology, Chair of Iorganic Chemistry I, Bergstraße 66, 01069, Dresden, Germany

Lithium-Sulfur Battery cells already exceed traditional Lithium-Ion-Battery cells in terms of specific energy. Values of 400 Wh/kg have been reported for >10 Ah Li-S cells and 243 Wh/kg for Li-Ion cells, respectively.[1] However, besides this tremendous advantage related to the cells’ weight, Lithium-ion cells still surpass the best Li-S cells in terms of volumetric energy density (676 Wh/l [2] vs. 350 Wh/l [3]). This is a decisive drawback, especially concerning automotive applications. Here, we report on the main limiting effects for increasing the volumetric energy density of the Li-S technology, namely availability of thin high-energy lithium-metal anodes, sulfur solubility in the electrolyte and, related to that, cathode density and thickness. Since commercial sources for thin lithium-metal anodes are rare, rolls of lithium-metal foils with widths of more than 100 mm cannot be purchased below thicknesses of 100 µm. Fraunhofer IWS developed a scalable process for manufacturing 5-50 µm thin lithium-metal films on thin copper foils. The process is based on the film formation by melt deposition from liquid lithium at 200°C. We realized the wetting of the liquid lithium on the substrate by applying a lithiophilic interlayer with approximately 100 nm thickness. Besides volumetric optimization on anode side, we realized the continuous manufacturing of high-density carbon/sulfur cathodes. In combination with our developments of electrolytes with low polysulfide solubility, we succeeded in the application of stable high-capacity cathodes with 0.5 g/cm3. These recent IWS developments were applied in prototype Li-S cells showing the potential of Li-S- cells for volumetric energy densities of up to 500 Wh/l.

References: [1] Oxis Energy: “Ultra Light Lithium Sulfur Pouch Cell”, Data Sheet, 2017. [2] Panasonic: “NCR18650B”, Data Sheet, 2012. [2] Fraunhofer IWS: “internal data”, 2017. Handling and processing of metallic lithium in the production of next generation battery cells

Joscha Schnella, Anna Kollendaa, Gunther Reinharta aTechnical University of Munich (TUM), Institute for Machine Tools and Industrial Management, Boltzmannstraße 15, 85748 Garching, Germany

In order to satisfy the customers’ need for reliable energy supply, higher capacities of battery cells are needed for electro mobility and stationary battery systems. Among the most promising approaches for high-energy battery compositions are prelithiated lithium- ion cells, lithium-based solid-state cells, and lithium-sulfur cells. All of these contain metallic lithium as a central component. The properties of metallic lithium, especially its high reactivity and adhesiveness, impose special requirements on the processing technologies. To enable a cost-effective and efficient cell production, the processing of lithium metal should be automated, including handling, confectioning, and quality assurance. At the same time, safety and regulatory standards must be met. In this presentation, we would like to show the results of our latest research on requirements for automated processing of metallic lithium in an industrial production environment for the above-mentioned battery cell concepts. Thereby, the whole life cycle of metallic lithium from purchase to processing to disposal is analyzed to enable experiments and pave the way for a safe, high quality and cost effective production of these cells. Our analysis includes processes, material related as well as economic, and quality aspects, following the process chain of metallic lithium from sourcing via battery production to the final battery cell. Based on these findings, we suggest potential handling and processing technologies, as well as quality measurements for the respective process steps and cell variants to pave the way to efficient metallic lithium processing production facilities. On the factors affecting the capacity depletion of lithium-sulfur batteries at the cycling and storage

V.S. Kolosnitsyn, E.V. Karaseva, E.V. Kuzmina, D.V. Kolosnitsyn

Ufa Institute of Chemistry of the Russian Academy of Sciences, Laboratory of Electrochemistry, Prospect Oktyabrya 71, Ufa, 450054, Russia

The characteristic peculiarity of lithium-sulfur batteries is fast capacity depletion during their cycling and storage. The rate of capacity decreasing determines the cycle life and the life time of lithium-sulfur batteries. In the most cases, cycle life is limited by several tens or hundreds of cycles that is not enough to the common usage of lithium-sulfur batteries. Fast capacity depletion during cycling and storage of lithium-sulfur batteries is caused by the peculiarity of electrochemical system of lithium-sulfur. Sulfur and lithium sulfide, the final product of its electrochemical reduction, are dielectric and in the solid state do not have electrochemical activity. Therefore, operation mechanism of lithium-sulfur batteries significantly differs from the mechanism of batteries based on the other electrochemical systems. Differences in the operation mechanisms of lithium-sulfur batteries are caused by: • the solubility of sulfur (active material of sulfur electrode) and lithium polysulfides (intermediate compounds generated at charging and discharging of lithium-sulfur batteries) in electrolytes; • the mobility of active materials of the positive electrode (sulfur and lithium polysulfides) in the volume of the electrode and the cell because of their solubility in electrolytes; • changing the phase state of active materials of positive electrodes at charging and discharging of lithium-sulfur batteries. Capacity depletion of lithium-sulfur batteries happens both during cycling and storage and is caused by the simultaneous action of several interconnected factors. The main reasons of capacity depletion of lithium-sulfur batteries are the destruction of components of electrolyte systems, sulfur redistribution in the volume of positive electrode, passivation carbon components of positive electrodes, lithium dispergation. The rate of capacity depletion of lithium-sulfur batteries is also determined by end voltage of charging and end voltage of discharging of cycling and value of charging and discharging current. The value of the contribution of different chemical, electrochemical and physicochemical processes in the total capacity depletion is determined by composition and properties of the components of the lithium-sulfur batteries (electrolyte, separator, positive and negative lithium electrodes) and cycling mode. Presented work review the main chemical and physicochemical process, leading to decreasing capacity of lithium-sulfur batteries at their usage and their contributions into total capacity depletion.

This work was supported by RFBR, research project No.16-29-06190. Stabilizing sulfur carbon cathodes-a biotechnology approach

Mark Griffiths

EndLiS Energy, La Jolla, California, USA

Contact: [email protected], www.endlisenergy.com

Abstract

Interest in batteries is at an all-time high for end users and battery developers. Battery powered devices are ubiquitous with modern day society, and batteries that can deliver more charge safely and cost less are hot commodities. Cost effective high-performance battery chemistries are having multibillion-dollar purpose built factories dedicated to producing them in mass. Electric vehicles represent a huge growth potential for high performance batteries[1] and this demand can theoretically be met with lithium sulfur battery technology. Although LiS batteries represent great promise, they suffer from low coulombic efficiency, low power density, low wh/L, high cost of stabilizing additives[2], rapid capacity decay and excessive use of expensive lithium. All of these problems limit the commercial usefulness of LiS cells.

This presentation will detail the development of a cost-effective lithium sulfur coin cell with stabilized charge cycling by utilizing biotechnology materials and processes. Topics covered will be:

a) Background in biotechnology products

b) Creating an LiS coin cell

c) Stabilizing an optimized LiS coin cell

The obtained experimental data shows that 500 charge cycles with minimal capacity decay can be obtained. Discussion on increasing battery kinetics and future studies on LiS battery development will be covered.

References: [1] M.K. Song, Y. Zhang, E. Cairns: “A Long-Life High-Rate Lithium Sulfur Cell: A Multifaceted approach to Enhancing Cell Performance”, Nano Letters 2013, vol 13, issue 12, pages 5891-5899. [2] I. Bauer, S. Thieme, J. Bruckner, H. Althues, S. Kaskel: “Reduced polysulfide shuttle in lithium-sulfur batteries using Nafion-based separators”, Journal of Power Sources 2014, vol 251, pages 417-422. Impact of adapted nitrate-free electrolytes on pouch cell performance

a a,b a,b a,b a a,b S. Dörfler , M. Piwko , C. Weller , P. Härtel , H. Althues , S. Kaskel aFraunhofer Institute for Material and Beam Technology (IWS), Winterbergstr. 28, 01277 Dresden, Germany bTU Dresden, Department of Inorganic Chemistry 1, Bergstraße 66, 01069 Dresden, Germany

Due to the high theoretical specific energy of the lithium-sulfur system [1] this chemistry is a promising candidate for next generation energy storage device. However, the cycling stability of realistic Li-S cells that comprise reasonable sulfur loadings, low amounts of electrolyte and a lithium metal anode is usually limited. This is a result of degradation reactions being significantly affected by soluble lithium polysulfides, the cathode discharge intermediates diffusing to the anode and leading to low charge efficiency, active mass / capacity loss as well as severe anode corrosion. For this reason the suppression of the shuttle mechanism is a high priority task. It can be accomplished by tailoring the electrolyte properties in that way, that the conversion mechanism is still enabled, but at the same time, minimal lithium polysulfide solubility is realized. Here, we show that electrolytes with low polysulfide solubility possess the ability to prevent self-discharge without the need for additives such as lithium nitrate causing gas evolution. Additionally, the volume/mass of inactive components in Li-S cells can be potentially decreased. By adjusting the electrolyte composition by combining a highly coordinating solvent (tetramethylene sulfolane, TMS) with an unreactive diluent (1,1,2,2-Tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, TTE), the retention of sulfur active material could be significantly improved. By using this TMS/TTE electrolyte, we could reduce the electrolyte amount to 2.0 µL/mg-S while achieving a comparable capacity of 1080 mAh/g-S and 245 Wh/kg on pouch cell level. Due to the fact that the TMS/TTE electrolyte has a relatively high mass density of about 1.5 g/cm³ alternative solvents were screened for substitution. A novel electrolyte recipe (patent pending) has been identified enabling discharge capacities of ca. 1181 mAh/g-S in the 5. cycle at a rate of C/10. A different reaction mechanism without the formation of long- chain PS at room temperature is observed. This novel electrolyte system was implemented in pouch cells as well. Electrolyte amounts as low as 2.8 µl/mg-S could be realized and an energy density of 362 Wh/kg is shown. In contrast to the DME/DOL-based PS dissolving electrolyte system, both described electrolytes allow cycling even under conditions of low electrolyte/sulfur ratio (2.0 – 4.5 µL/mg-S) in coin and pouch cell experiments. We established a symmetric cell set-up comprising a sulfur cathode and the corresponding Li2S anode as a tool in order to differentiate between cathode and anode degradation for the above mentioned electrolytes. These experiments confirm stable and reversible cathode conversion chemistry in TMS/TTE for more than 300 cycles.

References: [1] M.-K. Song, E. J. Cairns, Y. Zhang, Nanoscale 2013, 5, 2186–2204.

Characterization of reaction intermediates in Li/S battery via operando transmittance UV/Vis spectroscopy Qi He, Manu U. M. Patel, Anna T.S. Freiberg, and Hubert A. Gasteiger

Chair of Technical Electrochemistry, Department of Chemistry and Catalysis Research Center, Technische Universität München, Garching, Germany

The fundamental mechanistic understanding of Li-S redox-chemistry, which is critical for developing efficient and stable Li-S batteries, is still not fully established [1]. For example, in the commonly used ether-based electrolyte of 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME), the composition of the polysulfide intermediates is still under lively discussion. Using operando X-ray absorption spectroscopy (XAS) combined with linear 2- combination fitting, Cuisinier et al. [2] propose that the formation of S6 starts immediately at the very beginning of the 1st discharge plateau, reaches its maximum concentration at the transition phase between 1st and 2nd discharge plateau, and that its concentration decreases drastically only at the end of 2nd discharge plateau. Yet, by exploiting operando UV/Vis 2- 2- spectroscopy, Zou et al. [3] revealed that instead of S6 , only S4 can be clearly detected throughout the whole potential range from 3.4 VLi to 1.8 VLi. Moreover, Cuisinier et al. [2] also emphasized that the discharge capacity of Li-S batteries is mostly limited by the unreacted sulfur, as calculated from XAS spectra which suggest that up to 20-25% S8 is still left unreacted at the end of discharge. On the other hand, Gorlin et al. have observed little or no S8 at the end of discharge in their spatially-resolved operando XAS measurements [4]. These debates originate from the complex Li-S chemistry with its many different reaction intermediates and their (electro)chemical interconversion. While the solid sulfur species have been clearly detected by operando techniques (e.g., XAS, XRD, NMR), the characterization of soluble reaction intermediates remains challenging. To close this gap, Zou et al. [3] have examined the cyclic voltammogram of S-reduction on a gold mesh 2- electrode by operando UV/Vis spectroscopy, based on which they proposed S4 to be the dominant intermediate in DOL:DME. Yet, this CV of S-reduction on a gold electrode may not represent the chemistry governing the galvanostatic cycling with a S/C-composite electrode. We therefore present here a spectro-electrochemical cell (UV/Vis spectroscopy in transmittance mode) with electrochemical performance comparable to conventional cells, which enables us to quantitatively characterize the evolution of soluble reaction intermediates in an operating Li-S cell (using Beer-Lambert law). In addition, since most UV/Vis reference spectra of polysulfides in the literature were obtained in other solvents such as dimethyl sulfoxid (DMSO) [5] or tetraglyme [6], and since the absorption of the same chromophore may shift in different solvents, we have also established a series of polysulfide reference spectra to ensure a clear peak assignment for the stable polysulfides in DOL:DME that so far has not been reported. Acknowledgements: The authors would like to acknowledge the German Federal Ministry of Economy and Energy (funding number 03ET6045D). References: [1] M. Wild et al., Energy Environ.Sci., 8, 3477-3494 (2015) [2]M. Cuisinier et al. J. Phys.Chem.Lett., 4, 3227-3232 (2013). [3] Q. Zou and Y.-C. Lu, J. Phys. Chem. Lett., 7, 1518–1525 (2016). [4] Y. Gorlin et al., J. Electrochem. Soc., 162, A1146–A1155 (2015). [5] R. Bonnaterre and G. Cauquis, J. Chem. Soc. Chem. Commun., 293 (1972). [6] C. Barchasz et al., Anal. Chem., 84, 3973–3980 (2012). Operando characterization of a Li/S battery by coupling X-ray absorption tomography and X-ray diffraction

Guillaume Tonina,b,c, Alice Robbaa,c, Céline Barchasza, Gavin Vaughanb,Marco di Michielb Renaud Bouchetc, Fannie Alloinc

aFrench Atomic Energy and Alternative Energies Agency (CEA-LITEN), 17 rue des Martyrs, 38054 Grenoble, France bEuropean Synchrotron Radiation Facility, CS 40220, F-38043 Grenoble Cedex 9, France cUniv. Grenoble Alpes, LEPMI, F-38000, Grenoble, France

High capacity sulfur electrodes are expected to serve to high energy density low cost next-generation lithium rechargeable batteries. Li/S cells involve a series of complex chemical reactions between solid and soluble sulfur species in the electrolyte, causing severe morphological changes of the positive electrode upon cycling and poor practical performances [1]. High specific energy density also means high areal capacity and highly demanding depths of discharge for the lithium metal electrode during striping/plating cycles. As a matter of fact, morphology changes of both electrodes upon cycling are still key parameters for Li/S batteries which requires a lot of different investigations to understand these degradation phenomena and the involved mechanisms.

In particular, in situ and operando X-ray diffraction technique has proven to be an interesting characterization tool [2], providing qualitative and quantitative information on crystalline active species upon cycling, for example at the positive electrode. As well, X-ray absorption tomography allows changes in the global morphology of the electrodes to be studied upon cycling [3]. In this work [4], X-ray absorption tomography was combined with X-ray diffraction to follow operando the full cell behavior thanks to morphological and chemical information on the cell components, and then to understand their ageing mechanisms. Using X-ray diffraction technique, the temporal and spatial distribution of lithium, sulfur and Li2S could be followed within the cell, as a function of the state of charge. Using X-ray absorption tomography, the morphology of the cell components, especially electrodes, could be monitored as well. An important evolution was observed, linked to the “breathing” of lithium electrode during plating/striping. The highly heterogeneous behavior when plating lithium explains the poor reversibility of the negative electrode while cycling, especially when combined with high capacity sulfur electrodes.

As a perspective of this work, the combination of electrochemistry, absorption tomography and XRD allows the correlation of macroscopic and microscopic phenomena in whole batteries under true operando conditions. We believe that such a characterization tool could be applied by material scientists while designing and characterizing new solutions developed for Li/S cells. References: [1] C. Barchasz, F. Molton, C. Duboc, J.-C. Leprêtre, S. Patoux, F. Alloin, Anal. Chem. 2012, 84, 3973 [2] S. Waluś, C. Barchasz, R. Bouchet, J.-C. Leprêtre, J.-F. Colin, J.-F. Martin, E. Elkaïm, C. Baehtz, F. Alloin, Adv. Energy Mater. 2015, 5 [3] L. Zielke, C. Barchasz, S. Waluś, F. Alloin, J.-C. Leprêtre, A. Spettl, V. Schmidt, A. Hilger, I. Manke, J. Banhart, R. Zengerle, S. Thiele, Scientific Report, 5 (2015) 10921 [4] G. Tonin, G. Vaughan, R. Bouchet, F. Alloin, M. di Michiel, L. Boutafa, JF. Colin, C. Barchasz ; Scientific Report, 5 (2017), 2755 Sparingly solvating electrolyte design for high energy density Li-S Batteries

Kevin R. Zavadil, Sandia National Laboratories, Albuquerque NM 87185 USA

Creating a cost effective, high energy density, long cycle life transportation battery based on the lithium-sulfur electrochemical couple requires overcoming a series of scientific and technical challenges (1). These challenges include reducing the electrolyte volume fraction within the cell, increasing the sulfur loading in the cathode, reducing sulfur loss from the cathode and the subsequent redox shuttle of lithium polysulfides, and reducing excess lithium in the anode, all while maintaining the necessary kinetics to support facile charge transport. The Joint Center for Energy Storage Research (JCESR) is redesigning the lithium-sulfur battery using a combination of novel materials concepts to address these challenges. An example is the use of electrolytes that are sparingly solvating of the polysulfide reaction intermediates and that constrain sulfur at the cathode, reducing the quantity of electrolyte necessary within the cell (2).

Focus will be placed on the design of a select class of sparingly solvating electrolytes, their structure- function relationship, and their impact on cell performance. Solvent-in-salt electrolytes, loosely referred to as solvates, represent a class of electrolytes in which the saturated lithium polysufide concentration can be tailored to greatly reduce redox shuttling between cathode and anode. Polysulfide solubility restriction has been demonstrated to redirect sulfur reduction from a solution mediated to a semi-solid state path (3). A semi-solid state reaction pathway provides a method for managing the precipitation and redistribution of sulfur within the cathode, promising to enhance capacity retention. Experimental methods are developed to describe the extent of the solvate regime (solvent-to-salt ratio) in these electrolytes using NMR, Raman spectroscopy, and conductivity measurements. Solvates are found to function at compositions beyond those expected for full solvent coordination, raising questions as to details of the electrolyte structure and its impact on kinetics. Experimental data is complemented by molecular dynamics simulations to gain insight into electrolyte structure at low solvent levels. The challenge of integrating a protected lithium anode, electrolyte, and cathode architecture at the cell level to take advantage of the unique properties of these electrolytes will be discussed. The generality of redirecting the reaction pathway will also be discussed.

The author acknowledges the contribution of the Joint Center for Energy Storage Research Li-S team in this presentation. This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

1. Eroglu, D.; Zavadil, K. R.; Gallagher, K. G., J Electrochem Soc 2015, 162, A982-A990. 2. Cheng, L.; Curtiss, L. A.; Zavadil, K. R.; Gewirth, A. A.; Shao, Y.; Gallagher, K. G. ACS Energy Lett 2016, 1, 503−509. 3. Lee, C.-W.; Pang, Q.; Ha, S.; Cheng, L.; Han, S.-D.; Zavadil, K. R.; Gallagher, K. G.; Nazar, L. F.; Balasubramanian, M., ACS Cent Sci 2017, 10.1021/acscentsci.7b00123 Effects of Li-anion interactions on solubility of lithium polysulfides in ionic liquids

a,* b c d e Seiji Tsuzuki , Wataru Shinoda , S. Seki , Y. Umebayashi , T. Mandai , Kazuhide Uenof, Kaoru Dokkof, Masayoshi Watanabef a National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan b Graduate School of Engineering and School of Engineering, Nagoya University, Nagoya, 464-8603, Japan c Department of Environmental Chemistry and Chemical Engineering, School of Advanced Engineering, Kogakuin University, 2665-1 Nakano-machi, Hachioji, Tokyo 192-0015, Japan d Graduate School of Science and Technology Niigata University 8050, Ikarashi, 2-no-cho, Nishi-ku, Niigata 950- 2181, Japan e Faculty of Science and Engineering, Graduate School of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551, Japan f Dept. of Chemistry and Biotechnology, Yokohama National University, Yokohama 240-8501, Japan *E-mail: [email protected]

Room temperature ionic liquids attract much attention as promising electrolytes for Li-sulfur batteries owing to lower solubility of lithium polysulfide compared with ether based electrolytes. The measurements of the solubility of lithium polysulfide in ionic liquids show that the solubility depends on the choice of anion.[1,2] The solubility of lithium polysulfides - - in TFSA [(CF3SO2)2N ] based ionic liquids is much lower than the solubility in OTf (CF3SO3 ) based ionic liquids. The solubility in TFSA based ionic liquids is about 2 order lower than that in OTf based ionic liquids. Unfortunately, however, the cause of the lower solubility in TFSA based ionic liquids is not well understood. We have carried out molecular dynamics simulations of the mixtures of lithium polysulfide and ionic liquids and analyzed the intermolecular interactions between ions by ab initio molecular orbital calculations to elucidate the cause of the anion dependence of the solubility. The molecular dynamics simulations show that the Li cation and polysulfide anions were solvated by counter ions in the mixtures. The stabilization by interactions with neighboring ions in the mixture (the stabilization by dissolution) controls the solubility of lithium polysulfides in ionic liquids. The simulations suggest that the magnitude of the attraction between the Li cation and anion plays important role in determining the anion dependence of the solubility. The analysis of the intermolecular interactions of Li cation with TFSA and OTf anions show that the interaction of Li cation with TFSA anion is much weaker than that with OTf anion, which shows that the weak attraction between Li cation and TFSA anion is one of the causes of the low solubility of lithium polysulfides in TFSA based ionic liquids.

Acknowledgments This work was supported by the ALCA program of Japan Science and Technology Agency (JST).

Reference: [1] K. Ueno, J.-W. Park, A. A. Yamazaki, T. Mandai, N. Tachikawa, K. Dokko, M. Watanabe: “Anionic Effects on Solvate Ionic Liquid Electrolytes in Rechargeable Lithium−Sulfur Batteries”, J. Phys. Chem. C 2013, 117, 20509- 20516. [2] J.-W. Park, K. Ueno, N. Tachikawa, K. Dokko, M. Watanabe: “Ionic Liquid Electrolytes for Lithium−Sulfur Batteries”, J. Phys. Chem. C 2013, 117, 20531-20541. Thermal effects and diagnosis tools in multilayer cells for real applications

Monica Marinescua, Xiao Huaa , Ian Hunta , Peter Kovacikb, Yu Merlaa, Yatish Patela, Rajlakshmi Purkayasthab, Sylwia Walusb, Teng Zhanga, Gregory Offera aImperial College London, Department of Mechanical Engineering, London, SW7 2AZ , UK bOxis Energy, E1 Culham Science Centre, Abingdon, OX14 3DB, UK

The success of lithium-sulfur (Li-S) batteries as an energy storage solution depends not only on increasing its performance attributes, but also on understanding and controlling its behavior in realistic conditions. Crucially, the effect of temperature on battery performance must be understood in order for pack design and control tools to enable the best use of this chemistry’s potential. In this work we explore thermal effects within Li-S cells. Firstly, we study thermally-induced current inhomogeneity within a cell, and, by extrapolation, within a pack, which has been shown to have a significant effect on the performance of intercalation lithium-ion batteries[1,2]. Secondly, we test differential thermal voltammetry (the rate of temperature change vs rate of voltage change)[3] as a diagnostic technique for measuring shuttle contribution during charging.

Single layer cells connected in parallel but held at different temperatures are found to contribute significantly different currents amount to the external circuit. This effect could play a significant role in a cell, due to thermal inhomogeneities across its layers or in a module, between parallel cells. We further propose a new cell configuration for measuring the magnitude of current inhomogeneity for a particular current load. We show that, in order to model the performance of a Li- S cell under cycling, one must allow the parallel layers within to behave differently, constrained to have the same voltage, but not the same state of charge and/or temperature.

Further, we propose a new diagnostic technique to serve as the basis for a smarter on-line charging procedure. Li-S cells are usually charged up to a voltage cut-off, a time cut-off and/or a temperature cut-off. With the assumption that the shuttle is the main mechanism of heat generation, a thermally-coupled physical model is derived, based on a zero- dimensional model of the cathode[4]. We show that such a model captures the essential thermal behavior seen in experiments and use it to identify the true state of charge of the cell. Based on voltage and temperature measurements, and on model predictions, we discuss the choice of an ‘optimum’ charging time. This technique is potentially easy to implement in applications to increase the cycle life of Li-S cells.

References: [1] Y. Troxler, B. Wu, M. Marinescu, V. Yufit, Y. Patel, A. J. Marquis, N. P. Brandon, and G. J. Offer: “The effect of thermal gradients on the performance of lithium-ion batteries”, Journal of Power Sources 2014, 1018 – 1025. [2] B. Wu, V. Yufit, M. Marinescu, G. J. Offer, R. F. Martinez-Botas, and N. P. Brandon: “Coupled thermal-electrochemical modelling of uneven heat generation in lithium-ion battery packs”, Journal of Power Sources 2013, 544-554. [3] Merla Y, Wu B, Yufit V, Brandon NP, Martinez-Botas RF, Offer GJ 2016, Novel application of differential thermal voltammetry as an in-depth state-of-health diagnosis method for lithium-ion batteries, JOURNAL OF POWER SOURCES, Vol: 307, Pages: 308-319, ISSN: 0378-7753 [4] M. Marinescu, T. Zhang, and G. J. Offer: “A zero dimensional model of lithium-sulfur batteries during charge and discharge”, Physical Chemistry Chemical Physics 2016, 584-593. Is Li-S ready for commercial uptake? Market demand and competition

Dr Gleb Ivanov

Sigma Lithium Ltd, Harwell Oxford Science and Innovation Campus, Oxfordshire, OX11 0QX, UK

We look into the general roadmap of new battery electrochemistries that could replace current Li-ion chemistries. The demand in battery improvements is primarily driven by the global trend to replace fossil fuels in transportation: on roads, in air and on waterways. We take commercial view on the state-of-the-art in Li-S batteries, its technical strengths and weaknesses. Possible entry market niches are discussed as well as constrains and opportunities to break into larger markets including aerospace and electric vehicles. Though in the past few years we have made significant headway in moving Li-S closer to the market there are still gaps in the technology which does not allow for faster commercialisation. The main obstacles are in the gap between cycle life and energy density, between battery charge-discharge power and its safety. Despite all difficulties Li-S is likely to start making its way to the market in the next 2 to 8 years.

POSTER

Chemical‐Confinement of Polysulfide for High‐Performance Lithium–Sulfur Batteries

Zhenhua Sun, Guangjian Hu, Feng Li, Hui‐Ming Cheng

Institute of Metal Research, Chinese Academy of Science, Shenyang 110016, China, Email: [email protected]

Lithium–sulfur (Li–S) battery is regarded as one of the most promising next generation batteries due to the high theoretical capacity and energy density. However, Li‐S batteries still suffer from some significant challenges that hinder their practical application. Currently, the mainly solutions rely on the single physical or chemical confinement method. Although the physical confinement method could achieve good performance at the beginning, the performance often decreased rapidly in the subsequent cycles because employing this physical confinement alone is insufficient to tackle the polysulfides‐shuttle issue. Similarly, employing the chemical confinement of sulfur copolymer alone was also difficult to achieve good cycling and rate performance due to the poor conductivity nature. Here, we report a sulfur‐rich polymer@CNT hybrid cathode for lithium sulfur batteries by combining the physical and chemical confinement strategy. The partially filled CNTs not only facilitate electron and ion transfer during the charge–discharge process, but also accommodate sulfur volume expansion. Meanwhile, the sulfur copolymer raises the Li+ transfer rate by offering electrons of benzene ring and prevents dissolution of lithium polysulfide ions by forming Carbon‐Sulfur bonds. The combination of physical confinement of lithium polysulfide ions into hollow CNT and the strong chemical binding of Carbon to sulfur in sulfur copolymer suppresses sulfur loss during the discharge/charge processes, enabling a high specific capacity 1300 mAh g‐1 at 0.1C rate, a high‐rate capacity of 700 mAh g‐1 at 2C rate and excellent cycling stability for 100 cycles with a specific capacity of 880 mAhg‐1 and a capacity retention of 98% at 1C rate for the sulfur with 1, 3‐diisopropenylbenzene (DIB) confined in CNT (S‐DIB@CNT) cathode[1]. We believe that the dual‐confinement strategic approach presented here offers a novel means in fabricating sulfur copolymer–carbon matrix electrodes to further the commercial application of Li–S batteries.

The authors acknowledge financial support from the National Science Foundation of China (Grant Nos. 51521091, and U1401243), the Youth Innovation Promotion Association of the Chinese Academy of Sciences (No. 2015150)

References: [1] G. J. Hu, Z. H. Sun, C. Liu, H. M. Cheng, F. Li, et al. : “A sulfur‐rich copolymer@CNT hybrid cathode with dual‐ confinement of polysulfides for high‐performance lithium–sulfur batteries”, Advanced Materials 2017, 29, 1603835. Strategies for high-performance lithium-sulfur batteries using solvate ionic liquids

Shiro Sekia, Yuki Ishinoa, Keitaro Takahashia, Wataru Murataa, Yasuhiro Umebayashib, Seiji Tsuzukic and Masayoshi Watanabed aKogakuin University, Department of Environmental and Energy Chemistry, Faculty of Engineering, Hachioji, Tokyo, Japan bNiigata University, Graduate School of Science and Technology, Niigata, Japan cNational Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan dYokohama National University, Department of Chemistry and Biotechnology, Yokohama, Kanagawa, Japan

1. Introduction Mixtures of Li salts and glyme behave like ionic liquids (ILs) and are classed as “solvate ionic liquids” (SILs). SILs shows higher thermal and electrochemical stabilities in comparison with pure glyme, because the glyme molecule is strongly coordinated to Li+ and forms the stable + [Li(glyme)] complex cation. The dissolution of Li2Sx was suppressed in these systems and stable charge-discharge of the S/carbon composite positive electrode (PE) was achieved because of the low Lewis acidity of [Li(glyme)]+ and low Lewis basicity of [TFSA]–. In this study, the insertion and extraction behavior of Li on an S-PE in SILs were investigated by electrochemical tests. 2. Experimental G3 and LiTFSA were used to prepare the [Li(G3)1TFSA] SILs. The characteristics of the Li-S cells were investigated with [S-PE | [Li(G3)1TFSA] | Li metal NE] cells. The PE sheet was composed of S, Ketjenblack, and polyvinyl alcohol. Galvanostatic charge-discharge measurements were performed at 303 K and 3.3-1.5 V with a current density of 92.9 mA g–1-S (C/18). A charge- discharge test with a small current (C/100) was also conducted at 303 K for differential analysis. 3. Results and discussion Figure 1(a) shows the charge-discharge curves of the [S-PE | [Li(G3)1TFSA] | Li metal NE] cell at a current of 92.9 mA g–1-sulfur (1/18C). In this Fig. 1 Li-S battery performance of [S-PE | study, the initial discharge and charge cycles are [Li(G3)1TFSA] | Li metal NE] cells. defined as the first and second cycles, respectively. Utilization of greater than 50% indicated that partial reduction to Li2S occurred in this system (initial discharge capacity: 1,060 mAh g–1). The discharge curve contained two voltage regions at around 2.3 and 2.0 V, and the differential curve of the discharge at 1/100C is shown in Fig. 1(b). The three dQ/dV peaks (1.91 V, 2.03 V, 2.26 V) suggest that Li insertion took place over at least three steps. In the presentation, we will report effects of electrolyte and electrode for Li-S performances. References: [1] S. Seki, N. Serizawa, K. Takei, Y. Umebayashi, S. Tsuzuki, M. Watanabe: “Long-cycle-life Lithium-Sulfur Batteries with Lithium Solvate Ionic Liquids”, Electrochemistry, 2017, in press. Influence of the cation in lithium and magnesium polysulfide solutions in dependence of the solvent chemistry

G. Biekera,c, K. Jalkanena, D. Diddensb,c, J. Wellmanna, M. Koleka,c, M. Wintera,b, P. Biekera, c aMEET Battery Research Center, University of Münster, Corrensstr. 46, 48149 Münster, DE bHelmholtz-Institute Münster, Forschungszentrum Jülich GmbH, Corrensstr. 46, 48149 Münster, DE cInstitute of Physical Chemistry, University of Münster, Corrensstr. 28/30, 48149 Münster, DE

Lithium/sulfur batteries (Li/S) are frequently considered as one of the most promising post- lithium-ion battery systems, because the high specific capacity of sulfur drastically outranges the capacities of the commonly used Li-ion insertion cathodes. Although a lot of progress has been made, the full commercialization of Li/S is still hindered by self-discharge and capacity fading. Both of these issues are mostly related to the formation of soluble polysulfide intermediates during charge and discharge at the sulfur cathode. [1] At the Li metal anode dendrite formation and a high reactivity with the electrolyte lead to additional lifetime and safety concerns. In order to circumvent the issues at the anode but still maintain high specific capacities, magnesium/sulfur batteries are increasingly studied. In contrast to Li, the Mg metal anode is stable against many electrolytes and thus enables homogeneous Mg deposition and dissolution at Coulombic efficiencies of up to 100%. In addition, Mg is much cheaper and highly abundant. However, also the development of Mg/S batteries is limited by the formation and dissolution of polysulfides. [2] This work investigates how the formation, the solubility, and the disproportionation and dissociation equilibria of the polysulfides are determined by the cation coordination and the solvents’ relative dielectric permittivity and Gutmann donor number. Therefore, “Li2S8“ and “MgS8” solutions in DMSO, DMF, ACN, THF, DME, TEGDME, and Pyr14TFSI were characterized by UV/Vis spectroscopy. Additionally, the formation of the polysulfide species was studied by CV. The results are supported by quantum mechanical calculations. Varying the cation and the solvent reveals their mutual interplay in stabilizing different polysulfide species. [3]

Fig. 1.: UV/Vis spectra of “Li2S8” and “MgS8” solutions in THF and DMSO.

References: [1] L. Nazar: “Lithium-sulfur batteries”, MRS Bulletin 2014, 436 – 442. [2] Z. Zhao-Karger: “Performance Improvement of Magnesium Sulfur Batteries with Modified Non-Nucleophilic Electrolytes”, Adv Energy Mater 2015, 1401155. [3] G. Bieker: “Influence of the Cation in Lithium and Magnesium Polysulphide Solutions in Dependence of the Solvent Chemistry”, PCCP 2017, 11152 – 11162. Effect of amount of electrolyte on cycle life of lithium-sulfur cell. Modelling approaches

V.S. Kolosnitsyn, E.V. Kuzmina, D.V. Kolosnitsyn, E.V. Karaseva, L.R. Dmitrieva

Ufa Institute of Chemistry of the Russian Academy of Sciences, Laboratory of Electrochemistry, Prospect Oktyabrya 71, Ufa, 450054, Russia

One of the most important actual problems of developing lithium-sulfur batteries is the problem of cycle life. Several factors affect the cycle life of lithium-sulfur batteries: the amount of electrolyte, nature and properties of carbon materials, the interaction of electrolyte components and metallic lithium electrode, redistribution of sulfur in the volume of positive electrode and in all cell. This work presents main results of an experimental and theoretical study on the effect of the amount of electrolyte on the cycle life of lithium-sulfur batteries. The model, which considers the effect of the amount of electrolyte on the sulfur utilization and volume of pore space of positive electrode and allows to calculate changes of the capacity of lithium-sulfur batteries during cycling depending on the amount of passed electricity, is suggested. The results of experimental studies and calculations are well correlated to each other.

1.0 μl/mAh 1.0 μl/mAh Q, mAh/g(S) (a) Q, mAh/g(S) (b) 1.5 μl/mAh 1.5 μl/mAh 1600 2.0 μl/mAh 1600 2.0 μl/mAh 1400 3.0 μl/mAh 1400 3.0 μl/mAh 1200 4.0 μl/mAh 1200 4.0 μl/mAh 1000 1000 800 800 600 600 400 400 200 200 0 0 0 50 100 150 200 250 0 50 100 150 200 250 Cycle number Cycle number

Fig. 1: Capacity depletion of lithium-sulfur cell during cycling. Limitation by electrolyte quantity in the cell. (a) – experimental data and (b) calculated data.

Research is supported by the Russian Science Foundation grant №17-7320115. SoC estimation of LiS batteries using a combination of current integration and in-situ impedance spectroscopy

Erik Berendesa, Claudius Jehlea, Ulrich Potthoffa aFraunhofer Institute for Transportation and Infrastructure Systems IVI, Zeunerstraße 38, 01069 Dresden, Germany

Accurate state of charge (SoC) estimation on modern batteries is required to ensure safe and reliable operation as well as to take full advantage of the stored energy. On Li-ion-batteries, the most common approach for SoC-estimation is the combination of the open circuit voltage method (OCV) and coulomb counting. However, on LiS-batteries, the OCV-method can be afflicted by a large SoC-error due to the flat shape of the potential curves, long relaxation times and hence a multitude of non-unique OCV curves. Impedance spectroscopy is a common method for electrochemical battery characterization. Several studies have shown that the battery impedance depends on SoC [1][2]. Therefore, a method for SoC estimation based on the battery impedance is presented. For that approach, LiS-pouch-cells were studied by impedance spectroscopy in terms of SoC, temperature, relaxation time, current flow and ageing. From the results, a discrete frequency set was selected, where the impedance shows a significant sensitivity to SoC and only a slight sensitivity to the other mentioned parameters. A black box model was built, which derives the SoC by a premeasured reference relation between the impedance at the selected frequency and the SoC. The impact of temperature, relaxation time, current flow and ageing is considered by correction functions, which correct impedance variations due to the other mentioned parameters. The approach allows real- time SoC estimation during battery operation due to short measurement times and the combination with coulomb counting. The model was validated with a dynamic discharge current profile based on the New European Driving Cycle including recuperative charge steps. The SoC-error was less than ± 5%.

References: [1] V. Kolosnitsyn et al.: “A study of the electrochemical processes in lithium-sulphur cells by impedance spectroscopy”, Journal of Power Sources 196 (2011), 1478 - 1482. [2] Z. Deng et al.: “Electrochemical impedance spectroscopy study of a lithium/sulfur battery: modeling and analysis of capacity fading”, Journal of The Electrochemical Society 160 (2013), A553 – A558.

In-operando near sulfur K-edge X-ray absorption spectrometry of Li-S battery coin cells

Claudia Zecha, Olga Grätzb, Svetlozar Ivanovc, Philipp Hönickea, Yves Kaysera, Manfred Stammb, Andreas Bundc, Burkhard Beckhoffa aPhysikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin, Germany bLeibniz-Institut für Polymerforschung Dresden, Hohe Straße 6, 01069 Dresden, Germany c Technische Universität Ilmenau, Gustav-Kirchhoff-Str. 6, 98693 Ilmenau, Germany

Lithium Sulfur (Li-S) batteries are promising candidates for improved batteries offering up to 5 times higher capacity than conventional lithium ion batteries. For a better understanding of battery degradation processes in-situ and in-operando characterization techniques are required [1]. By means of in-operando near sulfur K-edge X-ray absorption spectrometry recorded during galvanostatic cycling with potential limitation (GCPL) measurements we could determine the different sulfur species for 8 cycles of a Li-S battery with DOL/DME (1:1 wt.%) 1 Mol TFSI electrolyte. In particular, the formation of polysulfides could be revealed. We used CR-2032 coin cell formed Li-S batteries modified with thin windows enabling the transmission of excitation and fluorescence radiation. Traceable X-ray spectrometric measurements were performed using radiometrically calibrated instrumentation in the PTB laboratory at BESSY II synchrotron radiation facility. While for the first cycles the polysulfides convert almost entirely we see for further cycles a permanent appearance.

Fig.1: Modified coin cell for NEXAFS studies

Fig.2: GCPL curve with C-rates of C/10 for discharge Fig.3: In-operando sulfur K-edge NEXAFS for the first and C/5 for charge, respectively Discharge

References: [1] M. Müller, S. Choudhury, K. Gruber, V. Cruz, B. Fuchsbichler, T. Jacob, S. Koller, M. Stamm, L. Ionov, B. Beckhoff, Spectrochim. Acta B 94-95, 2014, 22-26 Effect of cathode porosity on battery performance of high loading Li-S battery with solvate ionic liquid electrolyte

Ayumi Ando, Kenzo Obata, Yoshiharu Matsumae, Kazuhide Ueno, Kaoru Dokko, Masayoshi Watanabe

Yokohama National University, Department of Chemistry and Biotechnology,79-5 Tokiwadai, Hodogaya-ku, 240-8501, Yokohama, Japan

1. Introduction One of the critical problems for Li-S battery is the dissolution of lithium polysulfides into the electrolyte during the electrode reactions, resulting in poor charge-discharge cycle stability. To overcome this, we applied solvate ionic liquid (SIL) as an electrolyte, which achieved suppression of polysulfides-dissolution and stable cycles (up to now more than 800 cycles) [1] [2] without LiNO3 . However, in actual Li-S batteries it is not easy to achieve higher energy density than that of the conventional Li-ion battery. To improve energy density, increase of sulfur loading amount and reduction of electrolyte without lowering battery performance is indispensable challenges[3]. In this work, we achieved high sulfur loading using 3D current collector and elucidated how the porosity of the cathode affects the battery performance. We also investigated the effect of electrolyte volume of SIL. 2. Experiments The sulfur / carbon(KB) composite (S/C) were prepared by melt-diffusion strategy. The S/C was dispersed in carboxymethyl cellulose (CMC) aqueous solution with sulfur : KB : CMC = 60 : 30 : 10 (wt %). The obtained slurry was infiltrated into Al foam as a 3D current collector. Electrochemical properties of sulfur cathodes were evaluated with 2032 type coin cells assembled with [Li(G4)1][TFSA] as an electrolyte in an Ar-filled glovebox. 3. Results and discussion We prepared the cathodes loading 0.9-5.5 mg cm-2 of sulfur. The capacity using 2D current collector (Al foil), was greatly decreased with increasing sulfur loading amount (Fig. 1a). On the other hand, the capacity using 3D current collector showed ca. 1000 mAh g-1, even if the sulfur loading amount was 5.5 mg cm-2. However, Fig. 1 Battery performance using some cells showed low capacity (<400 mAh g-1) [Li(G4)1][TFSA] as an SIL electrolyte. a) Initial discharge capacities plotted regardless of sulfur loading. As shown in Fig. 1b, the against sulfur loading. b) Effect of capacity was greatly lowered when the porosity of cathode porosity in Al foam on the cathode was less than 30%. This phenomenon indicates initial discharge capacity. that the ionic flux in the cathode affects the performance of Li-S battery. We will also discuss the effect of electrolyte volume on the energy density of Li-S battery using the SIL. 4. Acknowledgement This research was supported by JST ALCA-SPRING of Japan. References: [1] K. Dokko et al., J. Electrochem. Soc., 160, A1304 (2013). [2] N. Tachikawa et al., Chem. Commun., 47, 8157 (2011). [3] M. Hagen et al., Adv. Energy Mater., 5, 1401986 (2015) Electrocatalysts for Lithium-Sulfur Energy Storage Systems

Mirko Antea, Şeniz Sörgela, Timo Sörgela, Andreas Bundc afem Forschungsinstitut Edelmetalle + Metallchemie, Katharinenstraße 17, 73525, Schwäbisch Gmünd, Germany bHochschule Aalen, Forschungsinstitut für Innovative Oberflächen FINO, Beethovenstraße 1, 73430, Aalen, Germany cTechnische Universität Ilmenau, Institut für Werkstofftechnik, FG Elektrochemie und Galvanotechnik, Gustav-Kirchhoff-Straße 6, 98693, Ilmenau, Germany

Li-S- (Lithium-Sulfur-) battery systems theoretically provide very high gravimetric (2600Wh/kg [1]) and volumetric energy density (2800 Wh/l [2]). Hence, Li-S batteries are one of the key technologies for both the upcoming electromobility and stationary applications. Furthermore, the Li-S battery system is potentially cheap and environmentally benign [3]. The technical implementation suffers from cycling stability, low charge/discharge rates and incomplete understanding of the complex polysulfide reaction mechanism [4].

The aim of this work is to develop an effective electrocatalyst for the polysulfide reactions, so that the electrode kinetics of the sulfur half-cell reactions will be improved. Accordingly, the overvoltage will be decreased and the efficiency of the cell will be increased. An enhanced electroactive surface additionally improves the charge and discharge rates. To reach this goal, functionalized electrocatalytic coatings are investigated to accelerate the kinetics of the polysulfide reactions.

To best of our knowledge no extensive screening of electrocatalysts has been conducted so far. In order to determine a suitable electrocatalyst, apparent exchange current densities of a variety of materials (Ni, Co, Pt, Cr, Al, Cu, ITO, stainless steel) have been evaluated in a polysulfide containing electrolyte by potentiodynamic measurements and Tafel plots. The samples have been examined by SEM after potentiostatic sulfur or lithium sulfide deposition.

Up to now, our work shows that cobalt is a promising material with good electrocatalytic properties for the polysulfide reactions. Furthermore, an electrodeposition from a modified Watt’s nickel electrolyte with a sulfur source seems to provide an autocatalytic effect, but the electrocatalytic behavior decreases after several cycles of the current-potential-curve.

References: [1] L. Liu, Y. Hou, Y. Yang, M. Li, X. Wang, and Y. Wu, “A Se/C composite as cathode material for rechargeable lithium batteries with good electrochemical performance,” RSC Adv., vol. 4, no. 18, pp. 9086– 9091, 2014. [2] X. Ji and L. F. Nazar, “Advances in Li–S batteries,” J. Mater. Chem., vol. 20, no. 44, pp. 9821–9826, 2010. [3] H. Xu, L. Qie, and A. Manthiram, “An integrally-designed, flexible polysulfide host for high- performance lithium-sulfur batteries with stabilized lithium-metal anode,” Nano Energy, vol. 26, pp. 224–232, Aug. 2016. [4] H. Pan et al., “On the Way Toward Understanding Solution Chemistry of Lithium Polysulfides for High Energy Li-S Redox Flow Batteries,” Adv. Energy Mater., vol. 5, no. 16, pp. 1–7, Aug. 2015. Si-C void structures as anodes in Li-S full cells – From coin cell to pouch cell level

a,b a a a,b Anne Baasner , Susanne Dörfler , Holger Althues , Stefan Kaskel

aFraunhofer Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany bDresden University of Technology, Department of Inorganic Chemistry, Bergstraße 66, 01062 Dresden, Germany

Silicon is an attractive alternative anode material increasing both the safety and the cycle stability of lithium-sulfur batteries [1]. It has the highest lithium storage capacity (3579 Ah -1 kg Li15Si4) among known elements and the delithiation occurs at a low voltage around 0.4 V vs. Li/Li+ [2]. During the lithiation process silicon undergoes a large undesirable volume expansion generally known from lithium alloys. This volume change leads to the degradation of the entire anode and fast capacity fading [3]. Nanostructured silicon carbon composites with free volume between the silicon core and a conductive carbon shell can potentially compensate the volume change and ensure a stabile solid electrolyte interphase (SEI) at the carbon surface preventing electrolyte consumption during cycling. In contrast to the recently published references, an easily scalable process without hydrofluoric acid etching treatment is presented in order to gain a free volume between silicon cores and the carbon shells (Figure 1).

Fig. 1: Schematic illustration of the synthesis process of the silicon-carbon composite

These silicon carbon void structures reveal a much higher capacity and cycle stability in half cells vs. lithium compared to bare silicon nanoparticles and Si-C composites without void structure. The feasibility of the prelithiated silicon-carbon anodes in lithium-sulfur full cells with ether based electrolytes was successfully shown both in coin cells and in pouch cells.

References: [1] J. Brückner, S. Thieme, F. Böttger-Hiller, I. Bauer, H. T. Grossmann, P. Strubel, H. Althues, S. Spange, S. Kaskel: “Carbon-based anodes for lithium sulfur full cells with high cycle stability”, Adv. Funct. Mater. 2014, 1284-1289. [2] J. K. Lee, C. Oh, N. Kim, J.-Y. Hwang, Y.-K. Sun: “Rational design of silicon-based composites for high-energy storage devices”, J. Mater. Chem. A 2016. [3] N. Liu, H. Wu, M. T. McDowell, Y. Yao, C. Wang, Y. Cui: “A yolk-shell design for stabilized and scalable li-ion battery alloy anodes”, Nano Lett. 2012, 3315. Rapid laser processing of open cell foams for battery applications

Robert Baumanna,b, Eckhard Beyera,b

aFraunhofer-Institut für Werkstoff- und Strahltechnik IWS, Winterbergstraße 28, 01277 Dresden, Germany bTechnische Universität Dresden, Institut für Fertigungstechnik, Georg-Bähr-Str. 3c, 01069 Dresden, Germany

Note that the global climate change is one of the largest challenges for the society of the 21th century. For managing the resulting consequences, innovative materials and production processes become more and more important for energy efficient applications. New innovative materials like open cell metal foams offer the solution concerning these challenges. Due to their surface-volume-ratio open cell metal foams offers increasable solutions concerning weight reduction of upcoming battery applications [1]. For battery applications the remote laser cutting offers a compromise between high productivity and used energy per manufactured electrode. Fraunhofer IWS investigations consider that this technique has a high potential concerning cutting speed, which was increased more than 500 % compared to state of the art laser separation. Quality aspects such as spatter formation and contour accuracy are the most important issues while cutting open cell foam material with lasers. The High output value of electrodes is one key factor for low cost battery systems. Mechanical separation techniques like punching are state of the art. Nevertheless, the mechanical force damages the edge of the foam concluding in a squeezing effect. Next to that high tool costs as well as tool wear limits the flexibility in adapting the contour. With a cutting speed up to 200 m/min the remote laser cutting offers an impressive solution in overcoming challenges like flexibility and high output value [2]. In this contribution, we evaluate the quantity aspect such as the achievable cutting speed for different open cell foam materials like copper and nickel. Therefore, single mode fiber laser in cw- mode and high dynamic beam manipulation systems (scanners) were utilized. Next to the productivity of the separation process, quality aspect like edge behavior, thermal effect zone and contour accuracy were investigated. With standardized measuring machines, the possible contour accuracy was determined. Significantly, remote laser cutting depicts a precision of less than ± 15 µm. Importantly, the size of the area, which was influenced and damaged by the laser radiation, was decreased to less than 100 µm.

450µm Background 250 1200µm

200

Cutting 150

edge 100

50 Cutting speed [m/min] Sample 0 2,4x106 3,2x106 4,0x106 4,8x106 5,6x106 max. Fluence F [J/m²] 0 Fig. 1: SEM image – top view of the cutting edge of copper foam (remote laser cut) (left); achievable cutting speed in dependence on max. Fluence F0 for copper foam with pore sizes of 450µm and 1200µm (right)

References: [1] M.Ashy: ” Metal Foams : A Design Guide “, 2000. ISBN-13:978-0-7506-7219-1 [2] R.Baumann et al: ” Investigations of Corrosion Resistance of Laser Separated Open Cell Metal“, Adv.Eng.Mater, 2017, DOI: 10.1002/adem.201700107 Fluorinated reduced graphene oxide as an artificial solid electrolyte interface on lithium surface

Jernej Bobnara, e, Matic Lozinšekb, Rémi Dedryvèrec, d, Christian Njelc, d, Boštjan Genorioe, Robert Dominkoa, d aNational Institute of Chemistry, Hajdrihova 19, SI-1001, Ljubljana, Slovenia bJožef Stefan Institute, Jamova cesta 39, SI-1000, Ljubljana, Slovenia cCNRS / Univ. of Pau& Pays Adour, Institute of Analytical Sciences and Physical Chemistry for Environment and Materials, UMR 5254, 64000, Pau, France dALISTORE - European Research Institute, 33 rue Saint-Leu, Amiens 80039 Cedex, France eUniversity of Ljubljana, Faculty of Chemistry and Chemical Technology, Večna pot 113, SI-1001, Ljubljana, Slovenia

Lithium metal batteries (LMB) are one of the most promising systems of future energy storage. The main drawback of LMB is that they suffer low Coulombic efficiency and low safety due to lithium metal high reactivity. The reactivity of lithium metal leads to the formation of heterogeneous solid electrolyte interface (SEI), resulting in lithium dendritic growth during electrochemical cycling. The lithium dendritic growth can be suppressed by different approaches including the preparation of an artificial SEI. An artificial SEI can be prepared by in situ technique with proper additive in the electrolyte such as LiNO3 [1], or by ex situ technique by coating the lithium surface before assembling the cell. However, an artificial SEI needs to be as thin as possible, highly Li-ion conductive and electronically insulative with high Young's modulus. Graphene derivatives are ideal materials for artificial SEIs due to their high Young's modulus [2]. In search of the novel artificial SEI, we have prepared fluorinated reduced graphene oxide (FG) dispersion and coated lithium metal surface. FG modified lithium electrodes were tested in symmetrical cell, lithium iron phosphate batteries and lithium sulfur batteries. The surface chemistry was characterized by XPS, while morphology characterization was done by SEM and FIB.

Acknowledgement The presented work is part of HELiS project which receives funding from the European Union‘s Horizon 2020 research and innovation programme under Grant Agreement No 666221.

References: [1] Aurbach, D.; Pollak, E.; Elazari, R.; Salitra, G.; Kelley, C. S.; Affinito, J. On the Surface Chemical Aspects of Very High Energy Density, Rechargeable Li–Sulfur Batteries. J. Electrochem. Soc. 2009, 156, A694. [2] Yan, K.; Lee, H.; Gao, T.; Zheng, G.; Yao, H.; Wang, H.; Lu, Z.; Zhou, Y.; Liang, Z.; Liu, Z.; et al. Ultrathin Two- Dimensional Atomic Crystals as Stable Interfacial Layer for Improvement of Lithium Metal Anode. Nano Lett. 2014, 14, 6016–6022. Density Functional Theory Study of LiNO3 Additive/Li Metal Interface for Li Sulfur Batteries: Insights into X-ray Photoelectron Spectroscopy

Mahsa Ebadia, Matthew J. Laceya, Daniel Brandella, C. Moyses Araujob

a Department of Chemistry - Ångström Laboratory, Uppsala University, Box 538, 75121 Uppsala, Sweden b Materials Theory Division, Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden

One of the additives that can help suppressing the redox shuttle mechanism in Li-S batteries is LiNO3 [1]. There have been several experimental studies performed on the effect of LiNO3 in Li-S batteries [2,3] but so far no computational study on this additive in the context of the Li-S battery. Therefore, in this study, density functional theory calculations have been used to investigate the electronic structure and stability of LiNO3 and a number of possible reaction species namely; N2, N2O, LiNO2, Li3N, and Li2N2O2 from the reduction of this additive on the surface of the Li-metal negative electrode (see Fig. 1a) [4]. In addition, solid phases of (cubic) c-Li3N and (hexagonal) α-Li3N under ambient pressure, are also considered on the surface of Li metal. The N 1s X-ray photoelectron spectroscopy core level binding energies of these systems are calculated (Fig. 1b) and compared with experimentally reported values in the literature. Besides, some possible factors controlling the core level binding energies shifts in the systems are addressed.

Fig. 1: a) The adsorbed molecules on the Li (100) slab with the side and top views of the supercells. b) The N 1s core level binding energies for the adsorbed molecules on the surface. Referen References: [1] Y. V. Mikhaylik: "Electrolytes for Lithium Sulfur Cells", U.S. Pat. 2008, 680. [2] D. Aurbach, E. Pollak, R. Elazari, G. Salitra, C.S. Kelley, J. Affinito: "On the Surface Chemical Aspects of Very High Energy Density, Rechargeable Li-Sulfur Batteries", J. Electrochem. Soc. 2009, A694–A702. [3] M. J. Lacey, A. Yalamanchili, J. Maibach, C. Tengstedt, K. Edström, D. Brandell: "The Li–S battery: an investigation of redox shuttle and self-discharge behaviour with LiNO3-containing electrolytes", RSC Adv. 2015, 3632–3641. [4] M. Ebadi, M. J. Lacey, D. Brandell, C. M. Araujo: "Density Functional Theory Modelling the Interfacial Chemistry of the LiNO3 Additive for Lithium-Sulfur Batteries by Means of Simulated Photoelectron Spectroscopy": DOI: 10.1021/acs.jpcc.7b07847. Development of all-solid-state Li-S cells at CIC Energigune

Gracia, I.a, Eshetu, G. G.a, Li, C.a, Júdez, X.a, Zhang, H.a, Armand, M.a, Rodriguez-Martínez, L.a

aCIC Energigune, Albert Einstein 48, 01510 Vitoria-Gasteiz, Spain

To date, there are still some challenges that difficult the industrial development of Li-S batteries. Among them, capacity fading and low sulfur utilization, which have origin in the insulating nature of sulfur, lithium polysulfides (LiPS) dissolution, shuttling and uncontrolled precipitation of Li2S, are the most limiting factors. In the anode side, Li-dendrite formation is the most important difficulty to overcome.

At CIC Energigune, we have been focusing our research activities towards all-solid-state Li-S cells using both polymer and composite electrolytes, as we believe they might provide a substantial advantage in comparison with liquid cells in terms of safety and energy density1. Our approach is focused on the electrolyte development, new cathodic materials and processing techniques in order to achieve high performing Li-S batteries.

The use of different lithium-salts2, polymer-rich composites with inactive fillers3 or the use of additives in the solid polymer electrolyte4 can improve the performance of all-solid-state Li-S cells, by means of the formation of a stable SEI or increasing the S utilization.

Furthermore, some groups have recently reported that inverse vulcanized copolymers of sulfur inhibit the fast capacity decay in the liquid Li-S cells, leading to cathode materials with long cycling life2. Here we report the first example of a sulfur copolymer employed in all- solid-state Li-S cell using a polymer electrolyte. Besides acting as a sulfur reservoir, p(S-DVB) copolymers3 can suppress capacity fading in the early stages of the cell life.

References: [1] C. Li, H. Zhang, L. Otaegui, G. Singh, M. Armand and L. M. Rodriguez-Martinez, Journal of Power Sources, 2016, 326, 1–5. [2] Judez, X., Zhang, H., Li, C., González-Marcos, J.A., Zhou, Z., Armand, M., Rodriguez-Martinez, L.M., J. Phys. Chem. Lett., 2017, 1956–1960. [3] Judez, X., Zhang, H., Li, C., Eshetu, G. G., Zhang, Y., González-Marcos, J.A., Armand, M., Rodriguez-Martinez, L.M., J. Phys. Chem. Lett., 2017, 3473–3477. [4] Eshetu, G. G., Judez, X., Li, C., Bondarchuk, A., Armand, M., Zhang, H., Rodriguez-Martinez, L.M., Angew. Chem., 2017. DOI: 10.1002/ange.201709305. [5] a) W. J. Chung, J. J. Griebel, E. T. Kim, H. Yoon, A. G. Simmonds, H. J. Ji, P. T. Dirlam, R. S. Glass, J. J. Wie, N. A. Nguyen, B. W. Guralnick, J. Park, Á. Somogyi, P. Theato, M. E. Mackay, Y.-E. Sung, K. Char and J. Pyun, Nat Chem, 2013, 5, 518–524. b) I. Gomez, D. Mecerreyes, J. A. Blazquez, O. Leonet, H. Ben Youcef, C. Li, J. L. Gómez-Cámer, O. Bundarchuk and L. Rodriguez-Martinez, Journal of Power Sources, 2016, 329, 72–78. Current collector influence on the performance of Li-S batteries

Olga Grätza, Ivan Raguzina, Soumyadip Choudhurya,b, Manfred Stamma,c , Leonid Ionova,d aLeibniz-Institut für Polymerforschung Dresden bLeibniz-Institut für Neue Materialien Saarbrücken cTechnische Universität Dresden, 01062 Dresden, Germany dUniversität Bayreuth, 95440 Bayreuth, Germany

Nowadays, Li-ion batteries are intensively used, and Li-sulphur and Li-air systems are under research, Li-sulphur being the closer one to commercialization. The research on Li-sulphur batteries is mainly focusing on the cathode material. In a lesser extent, the anode, the separator and electrolyte are studied [1]. The current collector has been rather neglected. The current collector is a conducting, usually metallic foil, on which the active material is applied. Its role is in mechanical support and faster transportation of the electrons. We investigated the influence of the current collector on the battery performance: specific capacity and cycling stability [2]. Several different materials have been compared and it has been proved that the choice of the current collector has a big influence on the cycling stability and overall cell performance. We also investigated the role of the experimental conditions and of additives (Si and SiO2) on the chemical stability of the current collector during cycling and on the performance of the entire cell. It turns out that Nickel is not the ideal material, but that Aluminium has advantages over other investigated collector materials. One can conclude that nickel is not the ideal material, though its performance is improved by the addition of silicon. Aluminium turns out to be the best among the tested materials.

References: [1] A. Manthiram, S.-H. Chung, and C. Zu, “Lithium-Sulfur Batteries: Progress and Prospects,” Adv. Mater., vol. 27, no. 12, pp. 1980–2006, Mar. 2015. [2] I. Raguzin, S. Choudhury, F. Simon, M. Stamm, and L. Ionov, “Effect of Current Collector on Performance of Li-S Batteries,” Adv. Mater. Interfaces, vol. 4, no. 3, p. 1600811, Feb. 2017.

Performance and Mechanistic Comparison of Mg-S and Li-S batteries

Joachim Häckera, Christian Dannera, Norbert Wagnera, K. Andreas Friedricha,b aGerman Aerospace Center, Institute of Engineering Thermodynamics, Pfaffenwaldring 38-40, 70569, Stuttgart, Germany bUniversity of Stuttgart, Institute for Energy Storage, Pfaffenwaldring 6, 70569, Stuttgart, Germany

Sulfur is one of the most promising cathode materials due to its high theoretical capacity of 1672 mAh g-1, its low cost and environmental friendliness. In combination with a negative lithium electrode (Li-S) a cell voltage of 2.4 V and an energy density of 2800 Wh l-1 can be theoretically achieved. Yet the use of lithium metal suffers from safety and cost issues due to dendrite formation and limited world occurrence, respectively. In contrast magnesium features significant advantages as it is abundant and shows no dendrite formation during cycling, which ensures superior safety. Furthermore the combination of a negative magnesium electrode and a positive sulfur electrode (Mg-S) offers a higher theoretical energy density of 3200 Wh l-1 at a cell voltage of 1.77 V. Contrary to the Li-S technology the Mg-S system is still in a very early stage of research (first report by Kim et al. in 2011 [1]) and suffers from fast capacity decay in the first cycles and poor overall cycle stability. Especially the search for a suitable electrolyte emerged to be difficult as it inter alia has to be non-nucleophilic and capable of reversible Mg deposition/stripping. Very recently Zhao-Karger et al. published a Mg(BH4)2-derived electrolyte with enhanced cycling properties [2] which allows further detailed investigation of Mg-S cells. As both systems rest upon similar electrochemical reactions they display many related properties but also significant differences in the underlying processes. Ensuring the comparability by an identical setup, Li-S and Mg-S cells are investigated by means of galvanostatic cycling, cyclic voltammetry and electrochemical impedance spectroscopy to identify the origin of the fast degradation of magnesium-sulfur batteries.

References: [1] H. Kim. et al: “Structure and compatibility of a magnesium electrolyte with a Sulphur Cathode”, Nat. Commun. 2011, 2, 427 [2] Z. Zhao-Karger: “New class of non-corrosive, highly efficient electrolytes for rechargeable magnesium batteries”, J. Mater. Chem. A, 2017,5, 10815-10820. Morphology of Li deposits in LiN(CF3SO2)2-glyme solvate ionic liquids

Yasushi Katayamaa, Kengo Shimaa, Naoki Tachikawaa, Kazuki Yoshiia, Nobuyuki Serizawaa, and Masayoshi Watanabeb aKeio University, Faculty of Science and Technology, Department of Applied Chemistry, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan bYokohama National University, Department of Chemistry and Biotechnology, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan

Dissolution of lithium polysulfides (Li2Sx) into electrolyte solutions is one of the issues, which must be resolved in order to realize rechargeable lithium-sulfur batteries. It has been reported that the solubility of Li2Sx is negligibly low in the equimolar mixture of LiN(CF3SO2)2 (LiTFSA) and glymes [1], called a solvate ionic liquid (SIL). On the other hand, a lithium anode is demanded in order to gain the high specific capacity and large energy density of rechargeable lithium-sulfur batteries. However, it is often difficult to obtain smooth Li deposits in conventional organic electrolytes. In the present study, the morphology of Li deposits was investigated in LiTFSA-tetraglyme (G4) SILs with different compositions using electrochemical quartz crystal microbalance, optical microscope and scanning electron microscope (SEM). Fine and granular Li deposits were obtained on a Cu substrate in 50.0-50.0 mol% LiTFSA-G4 SIL at the current densities lower than 2 mA cm–2 while coarse and whisker-like Li deposits were observed in 54.5-45.5 mol% LiTFSA-G4 SIL regardless of the current density, as shown in Fig. 1. The difference in the morphology of Li deposits was considered related to the Li species and/or the structure of the interface between the substrate and the SILs. Raman spectroscopy and potentiometric titration indicated that the Li species in 50.0-50.0 mol% LiTFSA-G4 SIL was + + – [Li(G4)] while those in 54.5-45.5 mol% one were both [Li(G4)] and [Li(TFSA)2] . The + – overpotential for reduction of [Li(G4)] was found to be larger than that of [Li(TFSA)2] , resulting in formation of fine and uniform nuclei of Li on a Cu substrate in 50-50 mol% LiTFSA- G4 SIL. The cycle performance of deposition and dissolution of Li on a Cu substrate was examined in a Cu | 50.0-50.0 mol% LiTFSA-G4 | Li cell using a coin-type cell with a three- dimensionally macroporous (3DOM) separator. The coulombic efficiency of 94% was obtained at a current density of ±0.5 mA cm–2 with an electric charge of 3.6 C cm–2 for deposition. This work was financially supported by the Advanced Low Carbon Technology Research and Development Program (ALCA) of the Japan Science and Technology Agency (JST). (a) 50.0-50.0 mol% LiTFSA-G4 (b) 54.5-45.5 mol% LiTFSA-G4

–2.0 mA cm–2

2 µm 2 µm

Fig. 1 SEM images of Li deposits obtained on a Cu substrate in (a) 50.0-50.0 mol% LiTFSA-G4 SIL and (b) 54.5- 45.5 mol% LiTFSA-G4 SIL at 25°C. Current density: 2.0 mA cm–2. Electric charge: 3.6 C cm–2. References: [1] K. Dokko, N. Tachikawa, K. Yamauchi, M. Tsuchiya, A. Yamazaki, E. Takashima, J.-W. Park, K. Ueno, S. Seki, N. Serizawa, and M. Watanabe: "Solvate Ionic Liquid Electrolyte for Li–S Batteries", J. Electrochem. Soc. 2013, 160(8), A1304-A1310. On the mechanistic role of nitrogen-doped carbons in Li-S cathodes

C. Kensya,b, P. Strubela,b, S. Doerflerb, H. Althuesb, E. Troschkea, F. Hippaufb, T. Jaumannc, L. Giebelerc, S. Kaskela,b a Fraunhofer Institute for Material and Beam Technology (IWS), Winterbergstraße. 28, 01277 Dresden, Germany b TU Dresden, Department of Inorganic Chemistry I, Bergstraße 66, 01069 Dresden, Germany c Leibniz Institute for Solid State and Material Research Dresden (IFW), Helmholtzstraße 20, 01069 Dresden, Germany Corresponding author: [email protected]

Lithium Sulfur (Li-S) batteries are a promising alternative for electrochemical energy storage devices of the near future. Still several challenges have to be addressed for the commercialization of the Li-S battery. The cycling stability of realistic Li-S cells that comprise reasonable sulfur loadings, low amount of electrolyte, and a lithium metal anode is usually limited. This is a result of dendrite formation and electrolyte decomposition. These degradation reactions at the anode surface are significantly affected by soluble lithium polysulfides, the cathode discharge intermediates, diffusing to the anode and leading to self- discharge and other side reactions. One possibility to minimize these effects is the application of novel conductive nitrogen- doped carbon materials. Nitrogen atoms are able to interact with polysulfides and suppress their undesired transport to the anode [1]. Moreover, nitrogen doping is discussed to act as a redox mediator for the reduction of polysulfides to Li2S as discharge product even though this mechanism is still not fully understood [2]. On the basis of an efficient, scalable templating process, a nitrogen-doped carbon with selective pore geometry was developed without using toxic chemicals (e.g. HF or Cl2) and the nitrogen content can be controlled by using different melamine:sucrose precursor ratios [3]. High values for the surface area (1600-1800 m²/g) as well as for the total pore volume (3.7 cm³/g) were realized. The Li-S cells showed stable cycling up to 240 cycles and capacities >1000 mAh/g sulfur (6.8 μl/mg-S electrolyte amount) in the first cycles. In-operando X-ray diffraction measurements during cycling showed nano-crystalline beta- sulfur and Li2S for both un-doped and nitrogen-doped porous carbon materials. The nitrogen doped carbon matrix principally enabled a highly reversible precipitation of Li2S on the conductive substrate. In contrast, the un-doped carbon material showed irreversible Li2S formation and comparably less reversible Li2S/beta-sulfur formation. Summarizing, the identification of suitable sulfur host materials for reasonable cycling performance and the understanding of the precipitation processes of the charge and discharge products during cycling, is an essential step to high energy density Li-S batteries.

References: [1] X. Wang, Z. Zhang, Y. Qu, Y. Lai, J. Li, „Nitrogen-doped graphene/sulfur composite as cathode material for high capacity lithium-sulfur batteries“, J. Power Sources 2014, 361-368. [2] L. Yin, J. Liang, G. Zhou, F. Li, R. Saito, H. Cheng “Understanding the interactions between lithium polysulfides an N-doped graphene using density functional theory calculation”, Nano Energy 2016, 203-210. [3] P. Strubel, S. Thieme, T. Biemelt, A. Helmer, M. Oschatz, J. Brückner, H. Althues, S. Kaskel, „ZnO Hard Templating for Synthesis of Hierarchical Porous Carbons with Tailored Porosity and High Performance in Lithium-Sulfur Battery” Adv. Funct. Mater. 2015, 287–297. Towards realizing high gravimetric energy density Li-S cells

Justyna Kreis, MSc.,

OXIS Energy LTD, E1 Culham Science Centre, Abingdon OX14 3DB, UK, [email protected], tel +44(0)1865 407017

The increased demand for higher energy density electrical storage devices has led to a large acceleration in Lithium-Sulfur (Li-S) battery development, both in academia and the commercial sector. Li-S has a theoretical capacity of 1672 Ah kg-1 of Sulfur, and a theoretical energy density of close to 2600 Wh kg-1[1,2]. Realising the potential of the Li-S couple is somewhat more complicated. Parasitic mass of a real cell reduces the practically achievable energy density dramatically. The pie chart below shows an example of a breakdown of a pouch cell component by mass. Clearly in real world batteries optimising the electrolyte loading is critical as this could account for around 50% of the Li-S cell mass (in comparison with Li-ion cells, where electrolyte stands for 11-15% of the total cell weight) . OXIS Energy has achieved an 18.5 Ah pouch cell at 400 Wh kg-1[3] via optimization of each component whilst maintaining a sulfur loading of higher than 70% in the cathode and a sulfur utilization of ~70%. Here we describe the development of some of the critical cell components affecting gravimetric energy.

Fig. 1: Chart showing the mass percentages of each component in a typical Li-S pouch cell.

References: [1] Link between Materials Chemistry and Cell-Level Design for High Energy Density and Low Cost Lithium- Sulfur Transportation Battery, Eroglu, Gallagher, JES 2015 [2] Ta r a s c o n, J-M., and Armand, M. Issues and challenges facing rechargeable lithium batteries. Nature, 2001,414(6861), 359-367 [3] https://oxisenergy.com/products/ Lithium electrode as one of the factors, limiting specific energy and cycle life of lithium-sulfur batteries

V.S. Kolosnitsyn, E.V. Kuzmina, E.V. Karaseva, A.L. Ivanov, A.R. Nurgaliev, S.E. Mochalov, L.R. Dmitrieva, D.V. Kolosnitsyn

Ufa Institute of Chemistry of the Russian Academy of Sciences, Laboratory of Electrochemistry, Prospect Oktyabrya 71, Ufa, 450054, Russia

One of the main problems, preventing commercialization of lithium-sulfur batteries, is short cycle life and low specific energy. Specific energy and cycle life of lithium-sulfur batteries are limited by several factors: the destruction of electrolyte on the lithium electrodes, the interaction of electrolyte components and metallic lithium electrode, redistribution of sulfur in the volume of positive electrode and in all cell, destruction of carbon frame of positive electrodes, passivation of the carbon particles by insoluble products of electrochemical reactions and so on. Present work considers processes on lithium electrodes, which affect specific energy and cycle life of lithium-sulfur batteries:  Interaction of metallic lithium with components of electrolyte systems. At charging and discharging of lithium-sulfur cells, metallic lithium direct chemically interacts with components of electrolyte systems and generates gaseous or/and solid compounds, insoluble in electrolytes, decreasing volume of electrolyte and its conductivity. That leads to decreasing active surface of electrodes in results of disturbing of uniformity of electrolyte systems and «drying» cells and as a result decreasing the capacity of lithium-sulfur cells.  Interaction of metallic lithium with sulfur and lithium polysulfides. Sulfur and lithium polysulfides (intermediate products of electrochemical reduction of sulfur and oxidation of lithium sulfide) are dissolved in electrolytes. Chemical interaction of metallic lithium with sulfur and lithium polysulfides, dissolved in electrolytes, and can leads to accumulation of sulfur as lithium sulfide on the lithium electrode and decrease capacity of lithium-sulfur cells.  Dispergation of metallic lithium. During charging of lithium-sulfur cells, moss and dendrite precipitations of lithium are formed. Generation of fine dispersed metallic lithium leads to increasing the surface area of metallic lithium and following the intensification of the chemical interaction of lithium electrode with components of electrolyte systems. Moreover, microparticles of metallic lithium electrode lose electronic contact with lithium electrode, because their surface is passivated, and cannot participate in electrochemical processes. To compensate the loss of lithium as fine dispersed precipitation the excess of metallic lithium is used in lithium-sulfur cells.

Research is supported by the Russian Science Foundation grant №17-7320115.

Abstract - Poster

Structural Investigations of Silicon Thin Film Anodes Deposited by a Roll‐to‐ Roll Vacuum Process

Steffen Straach1, Nicolas Schiller1, Claus Luber1, Olaf Zywitzki1, Markus Piwko2, Holger Althues2 1 Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, Dresden, Germany 2 Fraunhofer Institute for Material and Beam Technology IWS, Dresden Germany

The preparation of silicon anodes by magnetron sputtering in a roll to roll process has been demonstrated and exceptional results in very high capacity and good cycle stability of the anode layers were obtained. To get a better understanding of the inner mechanisms during lithiation and delithiation of the silicon anodes, the behavior of such layers with respect to volume effects and structural changes was investigated using SEM techniques, before and after charging and discharging. The results of these investigations will be shown in this poster and first ideas for futher optimization of the Si‐layers will be discussed.

Cathode materials containing covalently bond sulfur: an option for reliable sulfur fixation in low temperature Li-S and Na-S batteries? L. Medenbach & P. Adelhelm

Friedrich Schiller University Jena, Institute for technical chemistry and environmental chemistry (ITUC) & Center for energy and environmental chemistry (CEEC), Philosophenweg 7a, 07743, Jena, Germany

Keeping the active material inside the electrode is one of the major challenges for developing metal‐sulfur batteries with high energy density and cycle life. According to this, the use of sulfur containing polymers instead of elemental sulfur promises a good fixation, while the projected reaction remains as a conversion between sulfur and sulfides. The most discussed candidate is S‐Polyacrylnitril (S‐PAN) [1] with an active load of almost 20%. The material itself possesses electronic conductivity and therefore supports the charge transfer process. Cycling experiments show that even without membrane techniques or LiNO3‐additive almost no polysulfide shuttle takes place in cells using a S‐PAN composite cathode. Furthermore, initial capacities of more than 1200 mAh/g(S) are possible. Another, recently explored material class for electrochemical purpose are isopropylenebenzene based sulfur copolymers synthesized by inverse vulcanization method. Long‐chain polymeric sulfur can be stabilized by tethering it to a suitable cross‐linker [2,3]. So far, the electrochemical performance has been tested for Li‐ S batteries only. In this contribution the electrochemical properties of the mentioned materials are presented for room temperature Na‐S batteries as well. Differences and similarities to well investigated Li‐S analogues will be discussed.

References: [1] Zhang, S. S. Sulfurized carbon: a class of cathode materials for high performance lithium/sulfur batteries. Front. Energy Res. 1, 1–9 (2013). [2] Chung, W. J. et al. The use of elemental sulfur as an alternative feedstock for polymeric materials. Nat. Chem. 5, 518–524 (2013). [3] Simmonds, A. G. et al. Inverse vulcanization of elemental sulfur to prepare polymeric electrode materials for Li‐S batteries. ACS Macro Lett. 3, 229–232 (2014).

Microporous silicon oxycarbide derived submicrometric spheres as electrode materials for lithium sulfur and sodium ion batteries

Johannes Mundinga, Manuel Weinbergera and Margret Wohlfahrt- Mehrensb aHelmholtz Institute Ulm (HIU), Karlsruher Insitute of Technology, Helmholtzstraße 11, D-89081 Ulm, Germany, [email protected] b2Zentrum für Sonnenenergie- und Wasserstoffforschung (ZSW), Helmholtzstraße 8, D-89081 Ulm, Germany

Highly microporous carbon spheres with diameters of around 300 nm were synthesized via etching of a sol-gel derived silicon oxycarbide (SiCO) material with aqueous hydrofluoric (HF) acid solution. Unlike any other wet chemically etched SiCO, the resulting material shows a large BET surface area of 1133 m2g-1 and a total pore volume of 0.63 cm3g-1. Due to the etching, the carbon content increased from 35 wt% for the SiCO to 71 wt% for the HF etched material indicating that a large fraction of the silicon and oxygen were removed during the process. However with electron dispersive X-ray spectroscopy mapping (EDX) some silicon may still be detected, which may be attributed to carbidic species which are more stable towards the etching process. The porous material acts as an ideal host for elemental sulfur. Via melt impregnation a carbon-sulfur composite (50/50 wt%/wt%) was synthesized and characterized as a cathode for lithium sulfur batteries. Scanning electron microscopy (SEM) together with EDX clearly showed that the sulfur is homogeneously distributed within the carbon particles. Electrodes prepared from the composite (active material loading of ~3 mgcm-2) show good cycle ability at higher specific currents, for instance, at 500 mAg-1, capacities (related to the active material content) as high as 250 mAhg-1 (~500 mAhg-1 related to sulfur) may be retained after 100 cycles in an electrolyte consisting of a solution of 1M lithium triflate (LiTFI) and 0.2 M lithium nitrate (LiNO3) in a mixture (50/50 v%/v%) of 1,2- dimethoxyethane and 1,3-dioxolane. The coulombic efficiency quickly reaches values close to 100 % indicating an efficient confinement and good electrical contacting of the sulfur species within the micropores. The porous spheres were also tested as an anode in sodium ion batteries. Compared to the silicon oxycarbide precursor material, the carbon shows significantly improved electrochemical performance. For instance, at a specific current of 500 mAg-1, a capacity as high as 90 mAhg-1 may be retained after 100 cycles, whereas the silicon oxycarbide shows lower capacities around 80 mAhg-1.

Systematic study of binder species for high-performance lithium-sulfur batteries

Wataru Murataa, Keitaro Takahashia, Yuki Ishinoa, Masayoshi Watanabeb and Shiro Sekia aKogakuin University, Department of Environmental and Energy Chemistry, Faculty of Engineering, Hachioji, Tokyo, Japan bYokohama National University, Department of Chemistry and Biotechnology, Yokohama, Kanagawa, Japan

1. Introduction Lithium Sulfur (Li-S) battery is investigated to replace with lithium ion batteries. Sulfur, carbon and binder polymer are used as main component for composite positive electrode of Li-S batteries [1,2]. Specially, effects of binder polymer species are not clear. In this study, we focus effect of binder species in Li-S battery. 2. Experimental Positive electrode sheet of cells was composed of sulfur as the active material, Ketjenblack as the electrical additive, and Carboxymethyl cellulose (CMC) as the binder. These materials were mixed and thoroughly agitated with water, and (a) applied on to Al foil. Obtained electrode sheet showed strong binding ability, and achieved uniform electrode sheet without press-progress. Li foil and [Li(G4)0.8TFSA ＋ 4HFE] were used as negative electrode and electrolyte for test cells. The positive electrode loading was ca. 0.7 g/cm2. The prepared cells were analyzed by constant current charge and discharge mode at 303 K and 3.3 – 1.5 V with a current of 1/18 C. (b) 3. Results and discussion Figure 1 shows the cycle performances of charge/discharge test of the prepared cell. Obtained first discharge capacity was approximately 1000 mAh g-1. Capacity was also maintained of 600 mAh g-1 after 250 cycle (Fig. 1(a)) with high coulombic efficiency. Both high-capacity and easy-processing (c) (press-free, water-soluble binder) of Li-S battery were enabled by using the CMC binder into positive electrode materials. In this presentation, we will report systematic correlation of binder species for Li- S battery performances in detail.

References: [1] K. Dokko, et al, ‘’Solvate ionic liquid electrolyte for Li-S batteries’’, J. Electrochem. Soc., 2013, 160, A1304- A1310. [2] S. Seki, N. Serizawa, K. Takei, Y. Umebayashi, S. Tsuzuki, M. Watanabe: “Long-cycle-life Lithium-Sulfur Batteries with Lithium Solvate Ionic Liquids”, Electrochemistry, 2017, in press. Advanced MWCNT-based electrode for enabling high performance of concentrated electrolyte for Lithium-Sulfur batteries

Azusa Nakanishi, Yoshiharu Matsumae, Kazuhide Ueno, Kaoru Dokko, and Masayoshi Watanabe

Yokohama National University, Department of Chemistry & Biotechnology, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, 240-8501, Yokohama, Japan

One of the most serious problems for practical application of Li-S batteries is the dissolution of lithium polysulfides. Recently, highly concentrated electrolytes have attracted great attention due to their excellent ability for suppression of lithium polysulfides owing to their ionic-liquid-like low coordinating properties[1][2]. We have reported that the equimolar mixture of G4(tetraglyme) and Li[TFSA] (lithium bis(trifluoromethanesulfonyl)amide) ([Li(G4)][TFSA]), which is a type of highly concentrated electrolyte, behaves like an ionic liquid, consisting of the solvate cation ([Li(G4)]+) and the counter-anion ([TFSA]−), and thus is categorized as a “solvate” ionic liquid[2]. Since both the solvate cation and the anion behave as weakly coordinating ions in this electrolyte, the solubility of polysulfides is greatly suppressed, limiting the redox shuttle. As a result, Li-S cells with [Li(G4)][TFSA] shows high coulombic efficiency and good capacity retention[3]. However, since highly concentrated electrolytes have very high viscosity, transport into the microporous carbon structure of sulfur cathode may be limited, and Li-S cells with highly concentrated electrolytes tend to show lower discharge capacity than those with conventional electrolytes when such cathodes are employed. In this study, we report on the performance of Li-S cells with novel MWCNT/S cathodes. This strategy has the potential to improve the contact between the lithium ion containing electrolyte with the sulfur and electronical conductor (MWCNT), and thus may improve the energy density, and hence feasibility, of a concentrated electrolyte-based Li-S battery. We will elaborate about the cathode preparation and cell performance in the poster.

Acknowledgements This study was supported in part by Specially Promoted Research for Innovative Next Generation Batteries (SPRING) of the Advanced Low Carbon Technology Research and Development Program (ALCA) of the Japan Science and Technology Agency (JST). Authors acknowledge helpful discussions with Prof. Yasushi Katayama.

References: [1] S. Zhang et al: “Recent Advances in Electrolytes for Lithium-Sulfur Batteries”, Adv. Energy Mater. 2015, 1500117. [2] C-W. Lee et al: “Directing the Lithium-Sulfur Reaction Pathway via Sparingly Solvating Electrolytes for High Energy Density Batteries”, ACS Cent. Sci.2017, in press. [3] K. Ueno et al: “Glyme-Lithium Salt Equimolar Molten Mixtures: Concentrated Solutions or Solvate Ionic Liquids?”, J. Phys. Chem. B. 2012, 11323 - 11331. [4] K. Dokko et al: “Solvate Ionic Liquid Electrolyte for Li-S Batteries”, J. Electrochem. Soc. 2013, A1304 - A1310. Polyaniline coated cellulose separator for lithium – sulphur batteries

Nejc Pavlina, Silvo Hribernikb, Robert Dominkoa a National Institute of Chemistry, Department of Materials Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia b University of Maribor, Faculty of Mechanical Engineering, Smetanova 17, 2000 Maribor, Slovenia

Lithium sulphur batteries are attractive candidates for next-generation high-energy Li batteries. Their major drawbacks are rapid capacity degradation during cycling and low coulombic efficiency, caused by »shuttle effect« of soluble lithium polysulphides (Li2Sx, 4 ≤ x ≤ 8). Tailoring the physical and chemical properties of the separator has been proven to be a viable way to improve the performance of Li-S batteries. Vizintin et al. demonstrated that chemically modified reduced graphene oxide with hydrophobic properties or fluorinated graphene oxide improves capacity retention when used as interlayers on the separator in Li- S batteries [1, 2]. Due to high price of graphene it is necessary to find new materials with suitable property for application in battery systems. Cellulose nanofibers have many outstanding properties such as large surface area, easy modification, biodegradability, good mechanical properties and chemical durability. All these properties predict that appropriately modified cellulose nanofibers could be a promising material for the application as high performance Li-S separator. With aim to achieve suitable properties of cellulose separator, we coated cellulose fibres with polyaniline using simple oxidative polymerization [3]. Prepared membranes were characterized by FT-IR, SEM microscopy, thermogravimetric analysis, elemental analysis, and in electrochemical cell. The ability of polyaniline coated cellulose separator to prevent »shuttle effect« of soluble lithium polysulphides was studied by use of in-operando UV-Vis spectroscopy [4].

Financial support from the European Union Horizon 2020 research and innovation programme under Grant Agreement No. 666221 (HELIS) is acknowledged.

References: [1] A. Vizintin, M. U. M. Patel, B. Genorio, and R. Dominko: “Effective Separation of Lithium Anode and Sulfur Cathode in Lithium-Sulfur Batteries”, ChemElectroChem. 2014, 1040–1045. [2] A. Vizintin, M. Lozinšek, R. K. Chellappan, D. Foix, A. Krajnc, G. Mali, G. Drazic, B. Genorio, R. Dedryvère, and R. Dominko: “Fluorinated Reduced Graphene Oxide as an Interlayer in Li–S Batteries”, Chem. Mater. 2015, 7070–7081. [3] N. Gospodinova and L. Terlemezyan, “ Conducting polymers prepared by oxidative polymerization : Polyaniline”, Prog. Polym. Sci. 1998, 1443–1484. [4] M. U. M. Patel and R. Dominko, “Application of In Operando UV / Vis Spectroscopy in Lithium – Sulfur Batteries”, ChemSusChem 2014, 2167–2175. Evaluating lithium Poly(acrylic acid) as a water-soluble binder for high-loading sulfur cathodes in Li-S pouch-cells

Stefan Niesen, Manu U. M. Patel, Morten Wetjen, Hubert A. Gasteiger

Technical University of Munich, Chair of Technical Electrochemistry, Department of Chemistry and Catalysis Research, Lichtenbergstraße 4, 85748 Garching, Germany Contact: [email protected]; Phone +49(-0)-289-13857, www.tec.ch.tum.de

The lithium-sulfur (Li-S) battery is a promising post Li-ion technology, because of its high -1 theoretical gravimetric capacity of 1675 mAh g S. Yet, commercialization of the Li-S system is still hindered by the practically achievable energy density and the cycle life [1]. Increasing its attractiveness requires (i) to increase the areal capacity of the cathode to at least 4 mAh cm-2 [2], (ii) perform battery tests in a practical pouch-cell design [2,3], and finally (iii) replace the widely used N-methyl-2-pyrrolidone (NMP)-based polyvinylidene difluoride (PVdF) by a water-soluble binder, which is eco-friendlier and offers lower production costs [4]. In the current study, we investigate lithium (polyacrylic acid) (LiPAA) as an alternative, water-soluble binder for Li-S batteries with a high sulfur loading. Hence, we prepared sulfur -2 -2 cathodes with an areal capacity of 4 mAh cm (2.4 mgS cm ), consisting of 66 wt% sulfur, 24 wt% carbon black and 10 wt% LiPAA binder. For comparison, sulfur cathodes with a PVdF binder were also prepared through a conventional NMP-based procedure. In the first part, the two binder systems are characterized by means of their cycling stability and rate capability in a typical coin-cell setup at 25°C. Hence, Li-S half-cells were assembled by sandwiching three celgard separators soaked with electrolyte between a lithium metal anode and the different sulfur cathodes. 1 M LiTFSI and 0.25 M LiNO3 dissolved in a 1:1 mixture of 1,3-dioxolane and 1,2-dimethoxyethane (DOL:DME) was used as electrolyte. Further, the transport properties of the sulfur cathodes are discussed based on impedance measurements of symmetrical sulfur cells and Li-S half-cells. Building up on these results, we then demonstrate how the performance of the LiPAA-based 4 mAh cm-2 sulfur cathodes is affected by changing the cell design from standard coin-cells to lab-scale pouch-cells (~11 cm2) and discuss implications for the scale-up of aqueous-based binder systems for commercial Li-S batteries.

Acknowledgement: The German Federal Ministry for Economic Affairs and Energy is acknowledged for funding (“LiMo” project with funding number 03ET6045D).

References: [1] Z. Lin, C. Liang: “Lithium-Sulfur Batteries: from Liquid to Solid Cells”, Journal of Materials Chemistry A 2014, 936 - 958. [2] O. Gröger, H. A. Gasteiger, J.-P. Suchsland: “Review - Electromobility: Batteries or Fuel Cells?”, Journal of The Electrochemical Society 2015, A2605-A2622. [3] M. Hagen, D. Hanselmann, K. Ahlbrecht, R. Maça , D. Gerber, J. Tübke: “Lithium-Sulfur Cells: The Gap between the State-of-the-Art and the Requirements for High Energy Battery Cells”, Advanced Energy Materials 2015, 1401986. [4] J.-T. Li, Z.-Y. Wu, Y.-Q. Lu, Y. Zhou, Q.-S. Huang, L. Huang, S.-G. Sun: “Water Soluble Binder, an Electrochemical Performance Booster for Electrode Materials with High Energy Density”, Advanced Energy Materials 2017, 1701185. Operando XRD of advanced Li - S and Li - Ion batteries: What can we learn?

Ahmad Omara, Tony Jaumanna, Andreas Krauseb, Walter M. Weberb, Susanne Dörflerc, Holger Althuesc, Lars Giebelera a Leibniz IFW, Institute for Complex Materials, Helmholtzstr. 20, 01069 Dresden, Germany b NaMLab gGmbH, Noethnitzer Str. 64, 01187 Dresden, Germany c Fraunhofer IWS, Winterbergstr. 28, 01277 Dresden, Germany

Rechargeable batteries based on lithium-sulfur (Li-S) and advanced lithium-ion (LIB) technologies have garnered rapidly growing attention as potential energy storage systems in many applications such as electric vehicles, aircrafts and portable electronic devices owing to their high energy density and good reversibility. In order to improve life time, energy density and safety for a wider application, new technologies such as advanced separators, electrode designs or electrolytes not only have to be developed, but also need to be fully understood to allow further progress. Operando XRD is a powerful technique to identify degradation and failure mechanisms caused by phase transformation, conversion and strain within the electrode. It also allows to shed light on the kinetics of phase appearances and to determine appropriate conditions for cycling of batteries. Therefore, we have focused on real time characterization by operando XRD of several new technologies for Li-S batteries and post LIB batteries. In order to efficiently use the tightly limited, but highly required beam time at synchrotron facilities, an innovative sample changer was developed allowing high- throughput sample handling [1]. Herein, we will address some innovative technologies including functional separators, nitrogen doped sulfur cathodes and nanostructured silicon anodes implemented in conventional Li-S batteries (Fig. 1) to suppress the polysulfide shuttle effect and to extend cycle life by reduced electrolyte decomposition.[2] Additionally, novel electrolyte formulations in combinations with silicon anodes are studied. New findings help to optimize cycling conditions and electrode design.

Fig. 1: Operando XRD of a conventional Li-S cell over cycling at C/5 (top) and the integrated peak area of selected reflections of each observable phase according to electrochemistry (bottom).

References: [1] M. Herklotz et al.: “A novel high-throughput setup for in-situ powder diffraction on coin cell batteries”, J. Appl. Cryst. (2016). 49, 340–345. [2] A. Krause et al.: “High area capacity lithium-sulfur full-cell battery with prelithiated silicon nanowire-carbon anodes for long cycling stability”, Sci. Rep. 2016, 6, 27982. Lithium-sulfur battery; a new approach on the components for electric vehicles

F. Palombarinia, C. Auchera, A. Valdivielsoa aLeitat, Leitat Technological Center, C/de la innovació n°2, 08225 Terrassa (Barcelona, Spain) Phone: +34 93 788 32 00 - Fax : +34 93 789 19 06 - E-mail : [email protected]

Nowadays the constant demand for new ways of energy to replace lithium-ion battery due to its safety issues [1] has placed lithium-sulfur (LiS) on the spotlight of worldwide energy storage. Post Li-ion systems, in this particular case LiS batteries, are turning up for Electric Vehicle (EV) and Stationary applications. Therefore, a couple of years ago, ALISE (“Advanced Lithium Sulfur battery for xEV” – H2020 NMP17-2014, 666157), an European project which aim is the development of Li-S batteries, with a specific energy target of 400 Wh/kg, emerged. Presently, brand new materials are being developed and optimized regarding both electrodes, electrolyte and separator. At LEITAT, new electrolytes with different additives [2] are being studied (Fig. 1) in order to improve the performance of the battery such as specific capacity, cyclability and long chain polysulfides disolution. New ways of cathode composites synthesis are also being designed to avoid the loss of active material which results in a decay of capacity values and, concerning the separator, functionalization of the surface is being faced to enhance battery cyclability and to decrease the polysulfide shuttle effect.

80,00

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Solubility Li2S (mg/l) 20,00 10,00 Benzyl 2,2,2-trifluoroethyl sulfide Methoxy methyl phenyl sulfide Diphenyl sulfide 0,00 Methyl p-tolyl sulfide 0 Ethyl phenyl sulfide Fig. 1: Solubility10 of Li20S in DME:DOL with different percentage of additives 2 30 40 %wt Additive Fig. 1: Solubility of Li2S in DME:DOL with different percentage of additives

References: [1] N. Nitta, F. Wu, J. Lee, J. T. & G. Yushin: “Li-ion battery materials: present and future”, Mater. Today 2015, 252–264. [2] S. Gu, Z. Wen, R. Qian, J. Jin, Q. Wang, M. Wu, & S. Zhuo: “Carbon Disulfide Cosolvent Electrolytes for High- Performance Lithium Sulfur Batteries”, ACS Appl. Mater. Interfaces 2016, 34379-34386.

Room-temperature Na-S batteries - from coin cell to pouch cell level

Jonas Pampela,b, Michael Kohla, Susanne Dörflerb, Holger Althuesb and S. Kaskela,b

aFraunhofer Institute for Material and Beam Technology (IWS), Winterbergstraße 28, D-01277, Dresden, Germany bDresden University of Technology, Department of Inorganic Chemistry, Bergstraße 66, D-01062, Dresden, Germany

Due to the natural fluctuation in the electricity provided by renewable energy sources, stationary energy storages are needed to guarantee a stable energy supply. One very promising stationary energy concept are sodium sulfur (NaS) batteries due to the high abundance, low cost and high theoretical electrochemical capacity of both elements [1]. Since the 1980s, high temperature (HT) NaS-batteries are used as commercial energy storage, implementing electrodes in the molten state and a solid state electrolyte [2]. However, the HT battery design leads to a restricted utilization of sulfur’s theoretical capacity and the molten state of the electrodes causes not negligible safety problems. Both drawbacks can be overcome by operating NaS-cells at room temperature (RT). Admittedly, first literature results on RT-NaS indicate serious challenges regarding specific capacity, coulombic efficiency, and cycle life [3]. In the present work a special cell concept was developed to overcome those challenges (Fig. 1). First, a sodium-hardcarbon (HC) intercalation compound is formed in a carbonate based electrolyte. During this so-called sodiation process the electrolyte partially decomposes on the HC surface forming a solid electrolyte interphase (SEI). Second, the full cell is assembled with an ether based electrolyte employing the sodiated HC as anode and a sulfur-carbon composite as cathode. Applying the described concept, it was possible to achieve over 1500 stable cycles on coin cell level [4]. Moreover, latest result show the successful transfer of the concept from coin to pouch cell level indicating the feasibility of designing large scale stationary NaS-battery modules operating at room temperature.

Fig. 1: Concept for the preparation of stable sodium-sulfur cells operating at room temperature.

References: [1] X. Ji, and L. F. Nazar, Nat. Mater. 2009, 8, 500. [2] Z. Wen, and Z. Lin, Solid State Ionics 2008, 179, 1697–1701. [3] H. Ryu, and H.J. Ahn, J. Power Sources 2011, 196, 5186. [4] M. Kohl, F. Borrmann, H. Althues, and S. Kaskel, Adv. Energy Mater. 2016, 6, 1502185. Mesoporous Carbon and Nanofiber Interlayer as Efficient Polysulfide Reservoirs for High Performance Lithium-Sulfur Batteries

Tata N. Raoa*, E. Hari Mohana, Tejassvi Pakkia, Nanaji Katchalaa, Srinivasan Anandana a International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI) Balapur, Hyderabad-500005 Telangana, India. Tel: +914024452308 Fax:+914024442699 Email: [email protected]

Lithium-sulfur (Li-S) batteries have advantages of high theoretical capacity (1672 mAh/g) and high energy density (2600 Wh/kg) compared with Li-ion batteries, however, the issues like insulating nature of sulfur, polysulfide dissolution, and large volume expansion severely hamper its practical application [1]. In order to circumvent this, many attempts including the usage of various porous carbon materials, metal oxide composites, interlayer, electrolytes and their additives that can effectively trap the dissolved polysulfides, have been made so far [1,2], to enhance the electrochemical performance of Li-S batteries. In line with the on-going developments to overcome these issues, in the present study, we have explored a cost-effective bio-inspired highly graphitic mesoporous carbon and electrospun nanofibers as a matrix and interlayer, respectively, for the sulfur cathode. The resulting composite cathode and nanofiber interlayer show excellent electrochemical performance in terms of high capacity and improved stability as shown in Figure 1. The trapping of dissolved polysulfides and improving the ionic and electrical conductivities of electrode material by mesoporous carbon and nanofiber interlayer can be considered responsible for the promising performance of Li-S batteries in this study. The characterization and electrochemical studies of the materials will be discussed in detail during the presentation.

Fig. 1: Cycle performance of sulfur cathode with mesoporous carbon/sulfur composite (a) and nanofiber interlayer (b). Inset shows corresponding charge-discharge profile. References: [1] L. J. Wan: “Lithium-Sulfur Batteries: Electrochemistry, Materials, and Prospects,” Angew. Chem. Int. Ed. 2013, 13186-13200. [2] Tata N. Rao: "Graphene-Modified Electrodeposited Dendritic Porous Tin Structures as Binder Free Anode for High-Performance Lithium-Sulfur Batteries," Electrochimica Acta 2016, 701-710. Viscosity determination in polysulfide containing electrolyte for high energy lithium‐sulfur batteries

Brigitta Sieverta, Norbert Wagnera, K. Andreas Friedricha,b a German Aerospace Center, Institute of Engineering Thermodynamics, Pfaffenwaldring 38‐ 40, 70569 Stuttgart, Germany b University of Stuttgart, Institute for Energy Storage, Pfaffenwaldring 31, 70569 Stuttgart, Germany

The lithium‐sulfur battery is one of the promising systems for the future generation of rechargeable batteries. Its main advantages are the high theoretical capacity (1672 Ah/kg), high gravimetric energy density (2455 Wh/kg) and natural abundance. The insulating properties of sulfur as well as the formation of polysulfides in a complex reaction mechanism, which is not yet completely understood, are the main causes for battery degradation. In lithium‐ion batteries lithium ions intercalate from one crystalline matrix electrode to another. In lithium‐sulfur batteries lithium reacts directly with sulfur, but in a more complex way. Reaction takes place via electrolyte soluble polysulfide intermediates. After cell assembling of charged cell sulfur exists mostly in the orthorhombic crystalline form as cyclo– sulfur and a low percentage is dissolved in the electrolyte. During discharge, the partially dissolved sulfur reduces to polysulfide ions with progressively lower states of oxidation [1]. As the discharge proceeds, the dissolved sulfur in the electrolyte is consumed by electrochemical reactions, the concentration of sulfur decreases, while the concentration of shorter chain polysulfide is increasing. While lithium sulfide precipitates during discharge, the intermediate polysulfides are soluble in the electrolyte and are able to increase the electrolyte viscosity. During discharge the viscosity has reached its maximum at the endpoint of the first voltage plateau [2]. Efficient ion transport is an important parameter for fast rechargeable batteries. Ion conductivity or transport determines the performance of the rate capability of the secondary cells. Ion transport depends on two solvent properties: the viscosity and the dielectric constant. As shown by the Stokes‐Einstein equation, ion mobility is inversely proportional to the viscosity. As stated above lithium‐sulfur battery reaction takes place through electrolyte soluble polysulfide intermediates effecting electrolyte viscosity. It is important to highlight that the high reactivity of lithium sulfide is a problematic issue during measurements, because it hydrolyses easily in ambient air, producing hydrogen sulfide and lithium hydroxide. Therefore electrolyte viscosity of a polysulfide containing electrolyte cannot be measured in ambient air. In this work we show a method to measure electrolyte viscosity in an argon‐filled glovebox with sample quantities as small as 100 µL. We furthermore observe the degradation mechanisms of lithium‐sulfur batteries by enhancing the active loading of cathode while keeping constant the quantity of electrolyte for 1000 cycles.

References: [1] Canas, N.: Fabrication and Characterization of Lithium–Sulfur Batteries. PhD‐Thesis, Universität Stuttgart 2015 [2] S. S. Zhang, „Liquid electrolyte lithium/sulfur battery: Fundamental chemistry, problems and solutions,“Journal of Power Sources, 2013. Operando XRD data analysis of Li-ion batteries from laboratory diffractometers

Marco Sommarivaa, Milen Gateshkia, Thomas Degena, Detlev J. Götza, Fabio Masielloa, Kristin Gratzb, Matthias Hahnc, Michael Hahnc, Iris Zwanzigerc

aPANalytical BV, Lelyweg 1, 7602 EA, Almelo, The Netherlands bPANalytical GmbH, Nürnberger Str. 113, 34123 Kassel, Germany c EL-CELL GmbH, Tempowerkring 8, 21079 Hamburg, Germany

X-ray diffraction is a powerful tool for the characterization of battery materials [1,2]. Operando X-ray diffraction experiments of Lithium-Ion batteries are typically carried out at high brilliance synchrotron beamlines due to the possibility to use high-energy radiation which allows a very fast collection of diffraction data from rather thick batteries. However, a wealth of information can also be extracted by the analysis of diffraction data collected on a laboratory diffractometer, which is much more accessible compared to a synchrotron source. In this presentation we will show how high quality diffraction data of Lithium-based batteries can be quickly collected and analysed during charge/discharge cycles on a laboratory XRD diffractometer equipped with an X-ray tube with Silver or Molybdenum anode and an area detector optimized for high energy X-rays. Two main approaches will be demonstrated, in particular (a) transmission diffraction through single- and multi-layer pouch cells, and (b) reflection diffraction obtained with customized electrochemical cells which also allows the characterization of half cells.

References: [1] E. Talaie et al.: “Structure of the high voltage phase of layered P2-Na2/3− z [Mn1/2Fe1/2] O2 and the positive effect of Ni substitution on its stability”, Energy & Environmental Science 2015, 2512 - 2523. [2] Z. Liu et al.: “Local Structure and Dynamics in the Na Ion Battery Positive Electrode Material Na3V2(PO4)2F3”, Chemistry of Materials 2014, 2513 - 2521. Lithium surface modification: improving the cycling performances lithium- metal anodes

Marian Stana, Jens Beckinga, Martin Wintera,b and Peter Biekera aMEET Battery Research Center, University of Muenster, Corrensstrasse 46, 48149 Muenster, Germany bHelmholtz-Institute Muenster (HI MS), IEK-12, Forschungszentrum Juelich GmbH, Corrensstrasse 46, 48149 Muenster, Germany

Driven by the demand for higher energy density batteries, systems based on sulfur and oxygen as cathode materials with Li metal anodes hav e regained interest as candidates for beyond lithium-ion systems [1,2]. The existence of a native surface film and the formation of a solid electrolyte interphase (SEI) at the surface of the Li metal anode lead to heterogeneous and thus locally different current densities during the discharge and charge process, which can ultimately cause the formation of high surface area lithium (HSAL) during lithium deposition (charging) and hole/pit formation during dissolution (discharging) [3]. As a result of this behavior, Li metal anodes are characterized by poor cycling performance with low Coulombic efficiencies. Controlling the surface’s chemical composition and morphology represents one approach that has shown promising results to improve the electrochemical behavior of Li metal [4]. For example, thinning the surface native film was observed to improve the cycling performance of the Li metal anodes during the initial cycles (Fig. 1). However, this effect was gradually lost, due to the repeated depositions of fresh lithium and its irreversible reaction with the electrolyte. By creating artificial patterns on the micrometer scale, it is possible to spatially control the deposition of lithium, the dissolution-deposition overpotentials and the electrochemical performance [5]. This presentation will provide a comparison between various strategies able to overcome the intrinsic disadvantages of Li metal anodes and their effect on the overpotentials, cycling stability as well as on the formation of HSAL in such anodes.

Fig. 1: Schematic of the roll-press technique and its effect on the cycling performances of lithium-metal anodes

References: [1] H. Kim et al., “Metallic anodes for next generation secondary batteries“, Chem. Soc. Rev. 2013, 42, 9011. [2] W. Xu et al., “Lithium metal anodes for rechargeable batteries”, Energy Environ. Sci. 2014, 7, 513. [3] G. Bieker et al., “Electrochemical in situ investigations of SEI and dendrite formation on the lithium metal anode“, Phys. Chem. Chem. Phys. 2015, 17, 8670. [4] J. Becking et al., “Lithium-Metal Foil Surface Modification: An Effective Method to Improve the Cycling Performance of Lithium-Metal Batteries”, Adv. Mater. Interfaces 2017, 1700166 [5] M.-H. Ryou et al., “Mechanical Surface Modification of Lithium Metal: Towards Improved Li Metal Anode Performance by Directed Li Plating”, Adv. Funct. Mater. 2015, 25, 834. R&D of Fe-containing Li2S-based positive electrode material applicable for Li-S battery and analyses for its charge/discharge mechanism

Tomonari Takeuchia, Hiroyuki Kageyamab, Koji Nakanishic, Tomoya Kawaguchib, Toshiaki Ohtac, Toshiharu Fukunagab, Hikari Sakaebea, Hironori Kobayashia, and Eiichiro Matsubarab aNational Institute of Advanced Industrial Science and Technology (AIST), Midorigaoka 1-8-31, Ikeda, Osaka 563-8577, Japan bOffice of Society-Academia Collaboration for Innovation, Kyoto University, Uji, Kyoto 611-0011, Japan cRitsumeikan University, Noji-Higashi 1-1-1, Kusatsu, Shiga 525-8577, Japan

Lithium sulfide (Li2S) is one of the promising cathode active materials for high-energy rechargeable lithium batteries because of its high theoretical capacity (ca. 1170 mAh・g-1) [1]. However, this material is both electronically and ionically resistive, which gives rise to relatively low electrochemical performance in the cells [2]. Recently, we have tried to prepare Fe-containing Li2S-based positive electrode materials (Li8FeS5) and found that the cells showed the discharge capacity of ca. 730 mAh・g-1 [3]. However, its structure and charge/discharge mechanism were still unclear. In the present work, we analyzed the structure of Li8FeS5 using X-ray absorption (S K- edge XAFS; BL-10 in SR center of Ritsumeikan University) and X-ray scattering measurements (BL28XU in SPring-8) via pair distribution function (PDF) analysis [4,5]. The XRD pattern showed that the Li8FeS5 sample consisted of low-crystalline Li2S (antifluorite structure) [3]. The PDF analyses suggested that the structure of Li8FeS5 was explained by the antifluorite lattice where Fe atoms partially occupy Li sites, and such structure was formed in the course of the mechanical milling process within rather short time. During the charge, some structural rearrangements occurred by Li extraction, resulting in the formation of inhomogeneous distribution of S – S bonds and the loss of long-range atomic ordering. Such structures were reversibly recovered during the discharge when charged up to 2.6 V, whereas the structural reversibility was not observed when charged beyond 2.6 V. Such structural reversibility was responsible for the measured capacity value and retention during cycling. We also carried out the first principles calculations to simulate the structural rearrangements for Li extraction/insertion reactions, and the simulated results exhibited nearly consistent structural changes with those based on the above model.

Acknowledgements This work was financially supported by RISING2 project by METI and NEDO.

References: [1] A. Hayashi et al., J. Power Sources, 183, 422-426 (2008). [2] M. N. Obrovac and J. R. Dahn, Electrochem. Solid-State Lett., 5, A70-A73 (2002). [3] T. Takeuchi et al., J. Electrochem. Soc., 162, A1745-A1750 (2015). [4] T. Proffen et al., Z.Kristallogr., 218, 132-143 (2003). [5] K. Ohara et al., J. Phys.: Condens. Matter, 22, 404203 (2010).

Prototype battery cell processing at Fraunhofer IWS

P. Thümmler, P. Härtel, B. Schumm, T. Abendroth, H. Althues, S. Kaskel

Fraunhofer Institute for Materials and Beam Technology IWS, Winterbergstraße 28, 01217 Dresden, Germany

The lithium sulfur (Li-S) cell chemistry exhibits high potential due to its high gravimetric energy density. For demonstration, prototype pouch cell manufacturing is indispensable. In order to improve reproducibility and throughput of pouch cells, the level of automation need to be increased. For this purpose the critical production steps were automated as part of the Fraunhofer IWS process line, allowing a high level of machine-made assembly of Li-S pouch cells. Manufacturing of sulfur containing cathode films (C, S) are either carried out by roll-to-roll (R2R) slurry based wet coating, or by continuously laminating of dry films on a current collector (Al). Shaping of electrodes is done continuously by remote-laser cutting directly from coil. During this process, the cut outs are stored by using an automated handling system. The magazines of cut electrodes are subsequently implemented in a fully automated stacking machine, producing sheet by sheet stacked pouch cells in various dimensions. Within in this machine, the continuous cutting process for separators from coil, as well as an automated remote laser process for tab welding, is implemented. In the current state three different pouch cell formats are available to be machined at Fraunhofer IWS battery center. Small size (Pouch-S; 71x46 mm²; max. 5 Ah) and medium size (Pouch-M; 162x82 mm²; max. 24 Ah) are applied for Li-S cell chemistry. Pouch-PHEV1 size (195x143 mm²; max. 50 Ah) is applied for lithium ion cell chemistry. Summarized it can be stated, that by increasing automation level, reproducibility of pouch cell performance is further improved and the amount of waste reduced. The production of prototype pouch cells exhibiting up to 360 Wh/kg has been demonstrated so far.

Glass-type Li2S-P2S5 based electrolytes for next generation lithium sulfur batteries using novel composite cathodes

U. Ulissi1,2, A. Varzi1,2, S. Ito3, Y. Aihara3, S. Passerini1,2

1 Helmholtz Institute Ulm (HIU), Helmholtzstrasse 11, 89081 Ulm, Germany 2 Karlsruhe Institute of Technology (KIT), P.O. Box 3640, 76021 Karlsruhe, Germany 3 Samsung R&D Institute, Japan

The conversion reaction of sulfur to form lithium sulfide is characterized by a high theoretical energy density of c.a. 2500 Wh kg-1, a value 2.5 times higher than that of commercial state-of-the-art Li-ion cells [1]. Lithium-Sulfur batteries based on this conversion reaction may therefore represent the power source of choice for the future. The Li-S system is, however, still far from commercialization. In conventional organic electrolytes the conversion reaction is characterized by the formation of soluble polysulfides, resulting in the shuttling mechanism, causing low coulombic efficiency and high self-discharge rates[2]. This reaction is also associated with large volume changes. This can lead to cell failure, due to the alteration of the cathode and anode structure and the favored formation of lithium dendrites[3]. Moreover, sulfur and lithium (di)sulfide possess rather poor electron conductivity[3]. Glassy Li2S-P2S5 based solid electrolytes, characterized by a high ionic conductivity and chemical and electrochemical stability, are used to overcome the limitations of the systems employing liquid electrolytes[4]. The use of composite cathodes, incorporating carbonaceous materials and transition metal sulfides, can help improve cell performance by buffering volume changes, while creating effective electron conduction pathways and enhance sulfur utilization by catalytic effects. This work aims at demonstrating the feasibility of these Li-S all-solid-state batteries (Li-S ASSBs) employing said composite cathodes while elucidating some of the key concepts necessary for the realization of said devices. Li-S ASSBs show enhanced performances, with stable reversible capacities over -1 1.6Ah gS coupled with relatively high mass loadings.

Figure 1: Voltage profile of a Li-S all-solid-state cell, using a sulfur-carbon composite as the cathode and lithium metal as the anode(left). SEM micrograph of the cathode composite (right).

[1] M.S. Whittingham, History, Evolution, and Future Status of Energy Storage, Proc. IEEE. 100 (2012) 1518–1534. doi:10.1109/JPROC.2012.2190170. [2] A. Manthiram, Y. Fu, S.-H. Chung, C. Zu, Y.-S. Su, Rechargeable Lithium–Sulfur Batteries, Chem. Rev. 114 (2014) 11751–11787. doi:10.1021/cr500062v. [3] X. Liu, J.-Q. Huang, Q. Zhang, L. Mai, Nanostructured Metal Oxides and Sulfides for Lithium-Sulfur Batteries, Adv. Mater. (2017) 1601759. doi:10.1002/adma.201601759. [4] Y. Aihara, S. Ito, R. Omoda, T. Yamada, S. Fujiki, T. Watanabe, et al., The Electrochemical Characteristics and Applicability of an Amorphous Sulfide-Based Solid Ion Conductor for the Next-Generation Solid-State Lithium Secondary Batteries, Front. Energy Res. 4 (2016). doi:10.3389/fenrg.2016.00018. Infiltration of Sulfur in Microporous Carbon Aerogels

Frieder Wartha, Marina Schwanb, Norbert Wagnera, Barbara Milowb, K. Andreas Friedricha,c aGerman Aerospace Center, Institute of Engineering Thermodynamics, Pfaffenwaldring 38-40, 70569, Stuttgart, Germany b German Aerospace Center, Institute of Materials Research, Linder Hoehe , 51147 Cologne, Germany cUniversity of Stuttgart, Institute for Energy Storage, Pfaffenwaldring 6, 70569, Stuttgart, Germany

Lithium-Sulfur Batteries are one of the promising technologies for future energy storage. This technology has the potential of a specific energy density of 1675 mAh g-1, which is around two times higher than the energy density of common lithium-ion batteries. Further sulfur is an attractive active material due to its low cost and its environmental sustainability. However, the commercialization of Lithium-Sulfur batteries faces some challenges. Beside the insulating nature of sulfur and the usage of pure lithium as anode material, sulfur is soluble in the electrolyte and can therefore diffuse to anode. This phenomenon is called “shuttle-mechanism” and leads to a poor coulombic efficiency and a fast degradation of the cell. Different ways to suppress the shuttle-mechanism were investigated [1]. One way is to optimize the conductive carbon structure to hinder the sulfur diffusing to the anode. The use of carbon aerogels allows influencing pore size and geometry of the bimodal carbon matrix. With an additional melting or evaporating process after mixing carbon aerogels and sulfur it is possible to hold sulfur steric inside the pores. Another approach is to evaporate sulfur and trap S2 inside small nanopores (< 0.5nm) [2]. To optimize and understand the interaction of sulfur and porous systems different kinds of carbon aerogels and infiltration processes were combined and analyzed.

References: [1] L. Borchardt et al: “Carbon Materials for Lithium Sulfur Batteries – Ten Critical Questions”, Chem Eur J. 2016, 22, 7324 – 7351. [2] S. Zheng et al: “In Situ Formed Lithium Sulfide/Microporous Carbon Cathodes for Lithium-Ion Batteries”, ACS Nano. 2013, 7, 10995 – 11003. Freestanding and sandwich–structured electrode material with high areal mass loading for long life lithium–sulfur batteries

Mingpeng Yu,a Junsheng Ma,a Ming Xie,b Hongquan Song,a Fuyang Tian,a Shanshan Xu, a Yun Zhou,c Bei Li,b Di Wu,b Hong Qiua and Rongming Wanga a University of Science and Technology Beijing, Beijing 100083, People’s Republic of China. bBattFlex Technologies, Inc, Wuhan 430079, People’s Republic of China. cChongqing Normal University, Chongqing 401311, People’s Republic of China.

Lithium–sulfur (Li–S) battery has been vigorously studied due to its high theoretical energy density of about 2600 Wh kg1, low cost and environmental friendliness, potentially reshaping both electric transportation and the stationary electricity storage. The “polysulfide shuttle effect” (Li2Sn, 4≤n≤8) is the most pressing challenge that Li–S battery will encounter. The immobilization of sulfur/polysulfide ions is essential in improving the electrochemical performance. Herein, attempts to reconfigure the electrodes through multi–level forms of polysulfides control/interception have been made [1]. The resultant freestanding sandwich– structured architecture yields an extremely high loading of active sulfur up to 8.1 mg cm–2 in the multilayer capsule, which is much higher than the previously reported electrodes produced using the conventional slurry–coating method. Sulfur was firstly impregnated in nitrogen–doped graphene and constructed as primary active material, which was further welded in the carbon nanotube/nanofibrillated cellulose (CNT/NFC) framework. Interconnected CNT/NFC layers on both sides of active layer were uniquely synthesized to entrap polysulfide species and supply efficient electron transport (Fig. 1). The 3D composite network creates a hierarchical architecture with outstanding electrical and mechanical properties. Synergistic effects generated from physical and chemical interaction could effectively alleviate the dissolution and shuttling of the polysulfide ions. Electrochemical measurements suggest that the rationally designed structure endows the electrode with high specific capacity and excellent rate performance. Specifically, the electrode exhibited an areal capacity of ≈8 mAh cm−2 and an ultralow capacity fading of 0.067% per cycle over 1000 discharge/charge cycles at C/2 rate (1 C = 1675 mA g−1), while the average coulombic efficiency was around 97.3%, indicating good electrochemical reversibility. The superior electrochemical performance was closely related to its unique and well–defined structure. This novel and low cost fabrication procedure is readily scalable and provides a promising avenue for potential industrial applications.

Fig. 1 a) Digital photograph and b) 3D XRM image of the electrode. c) Out-plane SEM inspection. d) The rate performance of the electrode at various current densities References: [1] Mingpeng Yu, Junsheng Ma, Ming Xie, Hongquan Song, Fuyang Tian, Shanshan Xu, Yun Zhou, Bei Li, Di Wu, Hong Qiu and Rongming Wang, Advanced Energy Materials 2017, 1602347. Novel electrolyte approach and cell design for high energy Li-S cells

a,b a,b a a,b Christine Weller , Paul Härtel , Holger Althues , Stefan Kaskel

a Fraunhofer Institute for Material and Beam Technology IWS, Winterbergstraße 28, 01277 Dresden, Germany b Dresden University of Technology, Department of Inorganic Chemistry, Bergstraße 66, 01062 Dresden, Germany

The application of Lithium-Sulfur batteries is basically determined by its energy density. For reaching considerable energy density values above 350 Wh/L a special pouch cell design is required. It is generally accepted that reducing electrolyte volume to a minimum is essential for commercialization of the Li-S system as the electrolyte has currently the biggest weight share of the whole package. For efficient sulfur utilization as well as full cathode wetting with low electrolyte amounts, dense cathodes are inevitable to reduce porosity and therefore dead volume in the system. In our experience, the common catholyte-like electrolyte comprising of Lithium bistrifluoromethanesulfonimidate (LiTFSI) conductive salt in 1,2-Dimethoxyethane and 1,3- dioxolane (DME/DOL) ether combined with LiNO3 additive for shuttle suppression and solid electrolyte interface (SEI) formation is insufficient when combined with dense cathode showing low sulfur utilization and low cycle life as well as gasification and cell inflation. To overcome these drawbacks we introduced a novel systematic approach of limited polysulfide solubility e.g. using LiTFSI in a blend of sulfolane (TMS) and a hydrofluoroether 1,1,2,2-Tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE). By using this novel electrolyte, we could reduce the electrolyte amount to 2.0 µL/mg-S while achieving a comparable capacity of 1080 mAh/g-S (fig. 1). The latter is possible even without applying LiNO3 additive due to an intrinsic shuttle suppression based on the low polysulfide solubility with our electrolyte. Smooth lithium deposition on the lithium anode is facilitated and dendrite formation can be prevented, therefore impeding short circuits.

Variation of Electrolyt Amount: 2,3 A: 4.5 µL/mg-S (170 Wh/kg; 256 Wh/L) B: 2.0 µL/mg-S (245 Wh/kg; 363 Wh/L) (3.5 Ah Pouch Cell)

2,1 / V / / V /

1,9

voltage voltage 1,7

1,5 0 300 600 900 1200 capacity / mAh/g-S

Fig. 1: Discharge profiles for two identical Li-S pouch cells (3.5 Ah) with varied electrolyte amount (resp. cathode density) and the weight distribution of their components.

NOTES

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Organization

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