FROM NANO TO MESO

Eight Years of the DOE Energy Frontier Research Center

ARCHITECTURES Storing electrical energy is a central withdrawal. Storage saves solar FROM NANO TO MESO requirement to balance the energy or wind energy when available in AND BEYOND economy, providing compatibility abundance, and delivers it back SCIENCE TO ENABLE A NEXT GENERATION OF ENERGY STORAGE between where and when sources after sundown or when winds are Harvesting, holding, and delivering energy all rely on energy storage science. Batteries and related storage of energy are available and where calm. Batteries let us hold energy devices depend on both and electrons to move through materials and interfaces, providing challenges for materials science and chemistry in unparalleled ways. NEES seeks to understand these phenomena on a and when they are needed by users. in electric cars or cellphones and firm scientific footing and to develop new concepts to fuel a next generation of energy storage. Our collaboration Batteries and related energy storage use it when desired. Ideally, storage exploits a significant portfolio of experimental, theoretical, and intellectual resources. NEES achievements to date suggest boundless opportunities to create revolutionary designs for the batteries of the future. devices thus serve as an energy devices hold huge amounts of “bank,” receiving and holding energy energy and yet can deliver that that is deposited from various energy at high power. In a more sources, and delivering it to various subtle context, storage facilitates TODAY’S BATTERIES: NEES-1: NEES-2: • Uncontrolled transport paths • Precision nanostructured • Nanostructures beyond Li- uses when they need to make a smooth management of energy • Excess inactive material • Heterogeneous, multifunctional • 3-D mesoscale architectures • Safety concerns • / interfaces • Local consequences (ionics, degradation) supply and demand variations on • Rational design of interfaces & interphases the electric grid, and analogously

Particulate electrodes Precision heterogeneous during acceleration and braking in nanostructures for LIB an electric car. Enabling Today’s rechargeable lithium-ion methods

batteries—and those projected Interfaces and Single nanostructure Interphases over much of the next decade— platforms cannot meet the energy, power, FROM NANOSTRUCTURES ...... TO MESOSCALE reliability and safety demands in a ARCHITECTURES AND Nanostructure arrays growing energy economy. NEES THEIR CONSEQUENCES seeks to establish a scientific base Solid state energy storage Mesoscale architectures to support the paradigm shift in energy storage that is needed.

Degradation mechanisms EVOLUTION OF NEES RESEARCH The NEES mission is to reveal scientific insights and design principles that enable a next-generation electrical energy storage technology based on dense mesoscale architectures of multifunctional nanostructures. This mission has evolved substantially since NEES began in 2009.

1 NEES RESEARCH OUR TEAM MANAGEMENT TEAM THRUST 1 THRUST 2 THRUST 3 THRUST 4 • An Energy Frontier Research Center (EFRC) supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. Initiated in August 2009 (Phase 1),

renewed in 2014 (Phase 2) Gary Rubloff, Phil Collins, Chunsheng Reginald Penner, A. Alec Talin, UMD UCI Wang, UMD UCI Sandia, CA • +20 scientists funded in disciplines

ranging from chemistry and physics to 4 THRUST ENERGY SOLID STATE STORAGE materials and chemical engineering Synthesize solid and 3D solid state battery architectures to understand their electrochemical interfaces and consequences for performance of safe energy storage • Young energy scientists: graduate/

PhD students, undergraduates, Sang Bok Lee, Bryan Eichhorn, Liangbing Hu, John Cumings, Bruce Dunn, postdoctoral researchers UMD UMD UMD UMD UCLA Li+ • 7 universities and 2 national lab sites, SuSfrface LLayers Phashasee ChangeChange,,c cracks CNT led by the University of Maryland

• +250 journal publications over 8 years MnO2

Li15Si4 α-Si Au Sean Hearne, Kevin Leung, Mark Reed, Katherine Jungjohann, Henry White, glass Sandia, NM Sandia, NM Yale Sandia, NM University of Utah NEES IMPACT 37% THRUST 3 THRUST NANOSTRUCTURE DEGRADATION SCIENCE ADVISORY BOARD Chair: John Hemminger, UC Irvine Identify fundamental mechanisms driving nanostructure degradation and failure, and develop methods of mitigation Stephen Harris, Lawrence Berkeley National Laboratory Eric Joseph, IBM 28% V Tom Mallouk, Penn State University Elizabeth Lathrop, Chuck Martin, Janice Reutt-Robey, 23% YuHuang Wang, Kamen Nechev, Saft Groupe SA UMD UFL UMD UMD A Amy Prieto, Prieto Battery, Colorado State University 3 nnm MnO2 Lynn Trahey, Argonne National Laboratory, Joint Center for Energy Storage Research

Au glass Steve Visco, PolyPlus Battery Company Eric Wachsman, University of Maryland Energy Innovation Institute Nicolai Zhitenev, NIST CNST Zuzanna Siwy, Yue Qi, 7% 5% UCI Michigan State

THRUST 2 THRUST MESOSCALE ARCHITECTURES AFFILIATES

THRUST 1 10

30 Synthesize nanostructure assemblies into various architectures 0-5 >30 5- Hendrik Bluhm, LBNL 10-20

20- to assess the role of mesoscale architecture in realizing energy

Ethan Crumlin, LBNL S

CTA Kevin Zavadil, Sandia, NM SICS PNA Li+

SCIENCE CNT THRUST 3 Jabez McClelland, NIST NANO LETTERS

TURE MATERIALS TURE MATERIALS Jinkyoung Yoo, LANL SICAL CHEMISTRY SICAL CHEMISTRY TRY OF MATERIALS TRY CHEMICAL PHY

NA Li Si VANCED MATERIALS VANCED 15 4 PHY

α-Si

AD THRUST 4 ELECTROCHIMICA A TURE COMMUNICATIONS

CHEMIS Marina Leite, UMD NA

Y & ENVIRONMENTAL SCIENCE Y & ENVIRONMENTAL Yifei Mo, UMD CCOUNTS OF CHEMICAL RESEARCH CCOUNTS A ENERG

EXAMPLES OF JOURNALS IN THIS RANGE 1 THRUST IN TRANSPORT ELECTROCHEMICAL INTERPHASES Understand chemical formation of interphase films at electrochemical interfaces and their ion and electron transport 2 3 Arranging nanostructures into MESOSCALE architectures at the mesoscale ARCHITECTURES NEES has investigated the perfor- mance and stability of precision NEES’ focus on architecture is aimed at understanding the essential mechanisms underlying electrochemical nanostructures arranged in different events and battery performance—the benefits accessible through nanostructuring and 3D architectures. architectures, from highly ordered NEES’ research goals differ from that of much of the battery research community, where focus typically lies in (top left) to random (bottom). Both Ordered nanopore battery array, Ordered nanopores with lateral interconnects, understanding and identifying new materials for high performance battery chemistries. One of NEES’ research the dense packing of nanostructures C. Liu et al, Nat Nanotech (2014) Gillette et al, Physical Chemistry Chemical Physics (2015) goals is to provide nanostructure design guidelines that underscore the importance of electron transport for high energy density and the vari- pathways for access to ion storage material, amidst architectures involving porosity and tortuous pathways ability of local geometries in random through random, pseudo-random and regular 3D meso-architectures. Examples include parallel nanowires and arrangements may constrain ion and/ nanopores as an ideal case, sponge-like structures assembled in random 3D arrangement, and bio-scaffolds or electron transport and may intro- such as cellulose films and natural woods with highly anisotropic mesoscale pore design. duce sites that initiate degradation and failure. These are central issues of mesoscale science, which NEES seeks to address through comparing such structures, including particularly Pseudo-random arrangement of precision nanostructures into 3D “sponge” carefully synthesized models which COMPARATIVE architectures. Chen et al, ACS Nano (2012) ARCHITECTURES introduce elements of randomness A new (interpore connections, top right) in design distinguishes ion a controlled fashion. versus electron conductivity across a spectrum of meso- Battery architectures built on scale electrode architectures, Electrically conductive silicon Mesoporous cellulose fibers natural scaffolds offering insights into meso- carbon nanotube are functionalized with carbon composite yarn nanotubes and storage The structure of natural wood involves scale design guidelines and materials. possibly their propensity to densely packed micro- and nano-scale initiate degradation. pores clustered in different diameters, characteristics well suited to achieving the power-energy benefits of NEES’ 3D nanostructure arrays. NEES has developed processes to transform the wood to battery elements, carbonizing

and activating it to make a carbon Above: Cross sectional and top views of wood pores with MnO2 material added

anode, electrodepositing MnO2 to Below: Natural wood processed to form anode, cathode, and separator for a Li-ion battery. Amorphous MnO2 cathode High-temperature treatment nanowire arrays of grass forms carbonized make a cathode, and retaining the Chen et al, Energy & Environmental Science (2017) architecture framework for wood as is to make a separator, and battery anode. finally, demonstrating full battery performance. The benefits of wood’s unique 3D anisotropy are showing value across a broad spectrum, including green electronics, biological devices, transparent paper, solar cells, and functional membranes, as well as energy storage. Asymmetric supercapacitor

Templated growth 3D virus-templated of parallel silicon hierarchical electrodes nanowire forest 4 5 Passivation of reactive Li electrodes INTERFACES The pervasive growth of solid elec- AND INTERPHASES trolyte interphase layers in Li-ion batteries provides a complex passiv-

Building upon its recognized strengths in synthesis and characterization of heterogeneous nanostructures ating film containing inorganic Li2O and their assembly into meso-architectures, NEES has turned its attention to understanding mechanisms of and LiF (along with organic moeities). charge transfer at reactive interfaces, the evolution of new interphase films at these interfaces, and the resulting Nevertheless Li dendrites can form— charge transport through them. This research is advanced by development of new experimental platforms and risking battery shorting and fire—not by modeling and simulation intimately connected and relevant to the experiments. Experimental platforms push only in conventional Li-ion batteries, characterization to the deep nanoscale regime, revealing scaling behavior that ultimately controls electrochemical but surprisingly even in all solid state performance of nanostructured environments. Simulations with molecular scale fidelity depict reactions and the batteries. Using molecular modeling comparative kinetics of multiple pathways. The focus on reactive interfaces and resulting interphases has NEES has identified mechanisms by generated new directions, exemplified by the creation of an interface-free battery and the intentional formation which dendrite formation can be of artificial interphases that enhance electrode stability and battery capacity with cycling. initiated in the inorganics, particularly

Li2O, where Li atoms enter grain boundaries, provide electron transport paths, and ultimately result in passiv- ation breakdown via Li dendrites. Spatial Heterogeneities and Onset of Passivation. Breakdown at Lithium Anode Interfaces. These results inform the design of Leung and Jungjohann, J. Phys. Chem. C. (2017) passivation strategies in all solid state batteries.

Toward a perfect solid state battery

Rectification of ion transport through conical nanopores. Recognizing the myriad of challenges Vlassiouk et al, PNAS (2009) surrounding interfaces—particularly reactive interfaces that in turn form interphase films—NEES has conceived and demonstrated a solid state battery Precision coaxial nanowire as a charge transport testbed. made from particles of a single Corso et al, Nano Letters (2014) material, LGPS. Anode and cathode are formed by incorporation of carbon into those regions, enabling electron transport to support redox reactions Above: Conventional solid state battery in the LGPS itself to provide energy Below: Single-material solid state battery Binding sulfur to carbon nanopore surfaces. storage functionality. This “single Han et al, Advanced Materials (2015) Xu et al, Advanced Functional Materials (2015) material battery” based on LGPS and carbon effectively avoids interfaces between electrolyte and the electrodes.

Solvent-electrode surface reaction kinetics. Schroeder et al, ACS Appl. Mater. Interfaces (2015)

Revealing fundamentals of interphase formation. Li et al, Accounts of Chemical Research (2016)

6 7 Delithiation rates alter materials, DEGRADATION AND MITIGATION structures, and their properties. While silicon is highly desired as a Nanostructured electrodes enable enhancements in specific power and capacity for battery electrodes due to tremendous surface area and short ion transport pathways compared to their planar electrode counterparts. high energy anode, it poses severe However, nanostructures may be more susceptible to surface chemical processes (e.g., electrode dissolution, degradation problems due to its traditional solid-electrolyte interphase formation) and to consequences of cycling-induced structural changes large 300% volume expansion upon (e.g., nanoelectrode disconnection). In an effort to establish a science of electrochemical nanostructure full lithiation. Thin protective layers degradation, NEES has assessed its substantial research results to identify and categorize degradation are a promising approach to mitigate mechanisms—chemical, electrochemical, and mechanical. It has also developed and demonstrated critical the resulting fracture mechanics mitigation strategies that employ control of interface reactions and creation of interphases in the nano- problems. Using continuous reactive Slow Delithiation structured electrodes. Particular effort and success has resulted from close coupling of theory and experiment molecular dynamics simulation of to understand mechanisms, and to reflect this in design guidelines and predictive degradation models. silicon nanowirescoated by either

Al2O3 or SiO2, NEES has shown that fast delithiation leaves appreciable lithium inside the nanowire and imposes a radial gradient in mechan- Molecular dynamics model enables simultaneous tracking of chemical, ical properties, while slow delithiation structural and mechanical evolution of allows the nanowire to shrink and Si core-shell nanostructured electrode during lithiation. Kim et al, Physical expel most of the lithium, but leaves Chemistry Chemical Physics (2016) Chemical surface modification enables defect structures that accelerate heteronanostructure subsequent lithiation. These results designs to accommodate Delithiation rates modify composition, structure, provide guidelines for design and volume expansion & and properties of Si nanowire with strengthen interface protective coatings. Kim et al, Nano Letters (2017) Inert outer operation of silicon nanowire-based adhesion. Sun et al, ACS coatings prevent Nano (2013) battery anodes. structural instability while enhancing electron transport. Kharki et al, Managing high chemical reactivity ACS Nano (2013) in conversion material electrodes. Lithiation of high-energy electrode materials commonly causes dramatic NANOSTRUCTURE DESIGN CHEMICAL LiPON coated core double-shell Protection during conversion reaction DEGRADATION chemical reactions with new reaction AND products that render reversibility MITIGATION MECHANICAL ELECTROCHEMICAL (i.e., rechargeability) difficult. Using a

model MWCNT@RuO2 nanostructure, NEES has shown experimentally that Experimental TEM a thin protective layer of LiPON liquid cell platform provides insights to dramatically enhances the reaction microstructure reversibility during charge/discharge formations & propagations in cycles, allowing much more of the operando. Leenheer energy storage capacity of the nano- et al, ACS Nano (2015) electrodes to be retained. The use of Precision nanostructure a thin, conformal LiPON protective design offers valuable testbed Template-grown parallel layer is credited with some of this Conformal coatings of LiPON solid electrolyte on model MWCNT@RuO nanoelectrodes. to understand degradation, e.g. silicon nanowires demonstrate 2 nanostructures stabilization by spatial nonuniformities leading benefit because the thin LiPON Lin et al, ACS Nano (2016) to predictable locations for gel for liquid and solid state functions as a solid electrolyte in electrolyte systems. accelerated degradation and Le Thai et al, failure. Cho and Picraux et al, enabling Li-ion transport between (2013) ACS Energy Letters (2016) Nano Letters electrolyte and electrode.

8 9 Conformal thin solid electrolyte SOLID STATE ENERGY STORAGE Key opportunities in solid state A primary motivation for solid state batteries is to alleviate the safety risks associated with the flammable batteries lie in improved safety (no organic liquid electrolytes commonly used in rechargeable lithium-ion batteries, which have led to widely- flammable organic electrolyte), self- publicized fires and explosions. The use of all-solid-state materials also opens the door to significantly greater aligned 3D structures for high power- architectural design flexibility, enabling micro- and nano-electrode structuring in 3D and open-ended battery energy, and—potentially—conformal form factors. NEES research is focused on electrode and battery architectures as an overarching theme, solid electrolytes thin enough not to seeking to understand key aspects of solid electrode/electrolyte interfaces, including similarities and contrasts limit ion transport in the cell. NEES has developed ALD Li PO N, a LiPON-like with liquid electrolyte/electrode interfaces, and to develop synthesis approaches for solid state batteries on 2 2 solid electrolyte usable in the 40-100nm Above: Thermal ALD process for nano- and micro- scales. A particular emphasis is the synthesis of solid state electrolytes that can be deposited LiPON-like Li polyphosphazene conformally over micro- and nano-scale 3D topography to enable design flexibility and access the benefits thickness range in solid state batteries Right: Thin Li PO N solid electrolyte with challenging 3D topography— 2 2 of 3D architectures. Exploiting highly conformal atomic layer deposition, NEES has demonstrated solid in planar solid state battery. Pearse significant advances compared to ~1 electrolyte synthesis and its pivotal role in realizing the first fully 3D nanoscale solid state battery array. NEES et al, Chem Mater (2017) has also identified distinctly different applications for solid state batteries, exemplified by analog memory micron LiPON thickness employed in devices for neuromorphic computing. only planar, not 3D, configurations.

3D solid state batteries By distributing a given amount of active electrode material in thinner layers over larger surface area, energy density can be delivered at higher power, thereby achieving significant benefits from using 3D architectures in solid state batteries. NEES has demonstrated pioneering 3D solid state batteries. Sputter-deposited active layers exhibit rough topography and anisotropic materials. Multiphysics simulations show distinctive inhomo- geneities during charge and discharge. NEES’ expertise in precision Examining planar and 3D geometries lead Conformal ALD layers circumvent these hetero- nanostructures extends to novel to the development of conformal thin-film miniature solid state configurations. deposition techniques. Talin et al, ACS limitations, improving performance and Ruzmetov et al, Nano Letters (2012) Appl. Mater. Interfaces (2016) realizing the power-energy benefits of the 3D architecture.

Highly conforming, nanoscale, ion-conducting thin film is a key enabling factor for high density integrated 3D solid Sputter-deposited solid state battery layers over Si “pillar” scaffold. state batteries and for neuromorphic computing devices. Talin et al, ACS Appl. Mater. Interf. (2016)

Pearse et al, (submitted) Fuller et al, (2017) 10 Advanced Materials Advanced Materials 11 NEESCONNECT TRAVEL GRANTS NEES invests in multi-institutional, cross-disciplinary WHAT IS NEESCONNECT? STUDENT OPPORTUNITIES WHERE ARE THEY NOW? research collaborations. We create a cooperative NEESConnect is a community NEES encourages students to take learning environment to encourage active exchange of network of early career scientists on roles and initiatives that go science ideas and best practices, as exemplified by the who share common research inter- beyond their own research environ- 2016 NEES Collaboration Travel Grant initiative for ests and expertise in both basic and ment. They take on active roles early-career scientists. applied energy research areas.

WHAT IS OUR GOAL? Our overarching goal is to provide a sustainable program for workforce training and development in all NEES degree-graduates and (l-r) Martin Edwards (U of Utah), Juliette Experton (UFL), Yuxiao Lin (MSU), aspects of today’s complicated Zoey Warecki (UMD), Sylvia Xin Li (Yale) energy landscape—research, teaching, postdocs make contributions to science communications, outreach, many sectors of employment. energy policy and resources. THE TRAVELLING SCIENTIST CAREER PATHFINDER Travel offers early career scientists

(l-r, top row) Gaurav Jha (UCI), Luning Wang rewarding opportunities with lasting (UMD); (bottom row) David Ashby (UCLA), impacts. Emily Sahadeo (UMD) Zoey Warecki, a graduate student at such as the Student Thrust Leaders the University of Maryland studying to foster leadership skills and the materials science and EFRC newsletter writers to sharpen engineering, spent one communication skills. EFRC news- NEES has chosen an unusual research NEES foresees a bright future for these month visiting NEES letter writer and editorial board pathway to understand the science of approaches: dissecting ion and electron (l-r, top row) Erin Cleveland, Xinyi Chen, partners at the Center Stefanie Sherrill Wittenberg; (bottom row) member Tim Plett was a student at electrochemical energy storage, focused transport as manifested in architectures that Kostas Gerasopolous, Ashley Predith, Wenbo Yan for Integrated Nano- the University of California, Irvine. on structure (rather than materials) and underscore the importance of mesoscale technologies, part of embodied in the design of multicomponent, science and link nanoscience to battery- NEES hosts informal Q &A discus- Sandia National Laboratories. multifunctional nanostructures, their dense relevant length scales and behavior; interro- sion forums by inviting alumni She got hands-on experience with aggregation into mesoscale architectures, gating and representing these behaviors in student members to talk about developing and adopting the liquid and the consequences that follow. By models with predictive capability; combining their working experiences in the cell capability for transmission creating precision nanostructures— through modeling and nanoscale synthesis to achieve academic, industry and govern- electron microscopy to do battery novel synthesis approaches, closely coupled new levels of storage performance and ment sectors. research. with diverse modeling and characterization durability; developing a mechanistic science methods—NEES has elucidated fundamental of degradation which points the way to science ranging from the balance of ion mitigation strategies; realizing a profoundly and electron transport in electrode nano- safer battery technology; and applying these structures, to the impact of their assembly lessons to application domains beyond INTEGRATING INNOVATIVE IDEAS in larger-scale architectures, to degradation energy storage. The NEES student team devises new ideas to look at and mitigation phenomena that connect ion transport under confinement in battery research. mechanical, chemical, and electrochemical TO LEARN MORE VISIT www.efrc.umd.edu The team’s expertise converges in thin-film synthesis, behavior to nanostructure architectural semiconductor device fabrication and multiphysics Members: (l-r) Sylvia Xin Li, graduate student, Physics, Yale; design, and finally to design guidelines modeling to investigate transport properties in highly Kim McKelvey, postdoctoral researcher, Chemistry, U. of Utah; Nam Kim, graduate student, Chemistry, UMD; Chanyuan Liu, graduate student, that will benefit a next generation energy confined architectures. Materials Science Eng., UMD. storage technology.

12 WINNER OF 2017 PEOPLE’S CHOICE AWARD —EFRC-Hub-CMS Principal Investigators’ Meeting

Big Things, Small Packages By Chuck Martin (and the Nano Knights), NEES Principal Investigator, University of Florida

Big things come in small packages That’s the NEES nano way We can pulse more power Than anyone can say

Big things come in small packages We prove it true at NEES The architects of nanotech For your batteries The architects of nanotech For your energy needs

Ions, electrons, electrode materials too How you going to wire them to let the power come through? 3D nanostructuring that’s the thing we do To let the power come through To let the power come through Let the power come through! You best believe here at NEES we let the power come through

Because big things come in small packages That’s the NEES nano way Delivering the breakthroughs That lead to a brighter day

Big things come in small packages We prove it true at NEES The architects of nanotech For your batteries The architects of nanotech For your energy needs The architects of nanotech Here at NEES!

UNIVERSITY OF MARYLAND COLLEGE PARK www.efrc.umd.edu