Rechargeable Aqueous Batteries Based on Available Resources Investigation and Development towards Efficient Battery Performance Mylad Chamoun Academic dissertation for the Degree of Doctor of Philosophy in Inorganic Chemistry at Stockholm University to be publicly defended on Friday 15 February 2019 at 13.00 in Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B. Abstract Batteries employing water based electrolytes enable extremely low manufacturing costs and are inherently safer than Li-ion batteries. Batteries based on zinc, manganese dioxide, iron, and air have high energy relevancy, are not resource restricted, and can contribute to large scale energy storage solutions. Zinc has a rich history as electrode material for primary alkaline Zn–MnO2 batteries. Historically, its use in secondary batteries has been limited because of morphological uncertainties and passivation effects that may lead to cell failure. Manganese dioxide electrodes are ineffective as rechargeable electrodes because of failure mechanisms associated with phase transformations during cycling. The irreversibility of manganese dioxide is strongly correlated to the formation of the electrochemically inactive spinel, Mn3O4/ZnMn2O4. The development of the iron electrode for Fe–air batteries was initiated in late the 1960s and these batteries still suffer from charging inefficiency, due to the unwanted hydrogen evolution reaction. Meanwhile, the air electrode is limited in long-term operation because of the sluggish oxygen evolution and reduction kinetics. These limitations of the Fe–air battery yield poor overall efficiencies, which bring vast energy losses upon cycling. Herein, the limitations described above were countered for rechargeable Zn–MnO2 and Fe–air batteries by synthesizing electrode materials and modifying electrolyte compositions. The electrolyte mixture of 1 M KOH + 3 M LiOH for rechargeable alkaline Zn–MnO2 batteries limited the formation of the inactive spinels and improved their cycle life significantly. Further, the formation of the inactive spinels was overcome in mildly acidic electrolytes containing 2 M ZnSO4, enabling the cells to cycle reversibly at lower pH via a distinctive reaction mechanism. The iron electrodes were improved with the addition of stannate, which suppressed hydrogen evolution. Furthermore, optimal charge protocols of the iron electrodes were identified to minimize the hydrogen evolution rate. On the air electrode, the synthesized NiCo2O4 showed excellent bifunctional catalytic activity for oxygen evolution and reduction, and was incorporated to a flow assisted rechargeable Fe–air battery, in order to prove the practicability of this technology. Studies of the electrode materials on the micro, macro, nano, and atomic scales were carried out to increase the understanding of the nature of and interactions between of these materials. This included both in operando and ex situ characterization. X-ray and neutron radiation, and analytical- and electrochemical methods provided insight to improve the performance and cycle life of the batteries. Keywords: rechargeable aqueous batteries, alkaline electrolytes, aqueous sulfate electrolytes, zinc electrodes, manganese dioxide electrodes, iron electrodes, air electrodes, oxygen electrocatalysts. Stockholm 2019 http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-163154 ISBN 978-91-7797-552-6 ISBN 978-91-7797-553-3 Department of Materials and Environmental Chemistry (MMK) Stockholm University, 106 91 Stockholm RECHARGEABLE AQUEOUS BATTERIES BASED ON AVAILABLE RESOURCES Mylad Chamoun Rechargeable Aqueous Batteries Based on Available Resources Investigation and Development towards Efficient Battery Performance Mylad Chamoun ©Mylad Chamoun, Stockholm University 2019 ISBN print 978-91-7797-552-6 ISBN PDF 978-91-7797-553-3 Cover: Vector images adapted from Vecteezy.com & Freepik.com Printed in Sweden by Universitetsservice US-AB, Stockholm 2019 Doctoral Thesis 2019 Department of Materials and Environmental Chemistry Arrhenius Laboratory, Stockholm University SE-10691 Stockholm, Sweden Faculty opponent: Prof. Ann Mari Svensson Department of Materials Science and Engineering Norwegian University of Science and Technology (NTNU) Evaluation committee: Prof. Göran Lindbergh Department of Chemical Engineering and Technology The Royal Institute of Technology (KTH), Sweden Dr. Helena Berg CEO & Owner, AB Libergreen Prof. Daniel Brandell Department of Chemistry - Ångström Laboratory Uppsala University Substitute: Prof. Jiayin Yuan Department of Materials and Environmental Chemistry Stockholm University Cover: Investigated rechargeable aqueous battery chemistries for electrical power systems with renewable energy sources installed such as solar and wind power. List of publications This thesis is based on the following publications: Paper I: Effect of Multiple Cation Electrolyte Mixtures on Rechargeable Zn-MnO2 Alkaline Battery B. Hertzberg, A. Huang, A. Hsieh, M. Chamoun, G. Davies, K. J. Seo, Z. Zhong, M. Croft, C. Erdonmez, S. Meng, D. Steingart. Chemistry of Materials, 2016, 28 (13), 4536-4545 My contribution: Synthesized the MBDB material, contributed to the collection, and processing of the operando EDXRD data, conducted parts of the electrochemical characterization, and wrote parts of the manuscript. Paper II: Stannate Increases Hydrogen Evolution Overpotential on Rechargeable Alkaline Iron Electrodes M. Chamoun, B. Skårman, H. Vidarsson, R. I. Smith, S. Hull, M. Lelis, D. Milcius, D. Noréus. Journal of The Electrochemical Society, 2017, 164 (6), 1251-1257 My contribution: Conducted the electrochemical and structural characterization (SEM, XRD and EDS), contributed to the collection and processing of the operando neutron diffraction data, and wrote most of the manuscript except the XPS part. Paper III: 2+ Rechargeability of Aqueous Sulfate Zn/MnO2 Batteries Enhanced by Accessible Mn ions M. Chamoun, W. R. Brant, CW. Tai, G. Karlsson, D. Noréus. Energy Storage Materials, 2018, 15, 351-360 My contribution: Conducted the electrochemical and structural characterization (SEM, XRD, EDS and ICP-AES), contributed to data collection and the processing of the operando XRD data, performed the operando pH measurements and quantification of hydrogen on zinc electrodes, and wrote most of the manuscript except the TEM/EELS parts. Paper IV: Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron Electrodes A. R. Paulraj, Y. Kiros, M. Chamoun, H. Svengren, D. Noréus, M. Göthelid, B. Skårman, H. Vidarsson, M. B. Johansson. Batteries, 2019, 5, 1-15 My contribution: Contributed to data collection and processing of quantifying hydrogen on iron electrodes and wrote parts of the manuscript. i Paper V: Bifunctional Performance of Flow Assisted Rechargeable Iron-Air Alkaline Batteries M. Chamoun, A. R. Paulraj, B. Skårman, H. Vidarsson, Y. Kiros, D. Noréus. In manuscript My contribution: Synthesized the oxygen electrocatalysts (except LCMO), conducted the electrochemical and structural characterization (SEM and XRD), developed the Fe–air cell setup, and wrote most of the manuscript. Publications not included in this thesis: Paper VI: Water Splitting Catalysis Studied by using Real-Time Faradaic Efficiency Obtained through Coupled Electrolysis and Mass Spectrometry Svengren H., Chamoun M., Grins J., Johnsson M. ChemElectroChem, 2017, 5 (1), 44-50 Reprints were made with permission from the publishers. ii Contents List of publications ................................................................................................................................... i Abbreviations .......................................................................................................................................... v 1. Introduction .................................................................................................................................... 1 1.1. Large-scale energy storage systems ....................................................................................... 1 1.2. Electrochemical energy storage .............................................................................................. 2 1.3. Rechargeable aqueous batteries based on available resources ............................................. 2 1.4. Investigated electrode materials for rechargeable aqueous batteries .................................. 3 1.4.1. Zinc .................................................................................................................................. 3 1.4.2. Electrochemical challenges of zinc ................................................................................. 4 1.4.3. Manganese dioxide ......................................................................................................... 5 1.4.4. Electrochemical challenges of manganese dioxide ........................................................ 7 1.4.5. Iron .................................................................................................................................. 8 1.4.6. Electrochemical challenges of iron ................................................................................. 9 1.4.7. Oxygen electrocatalysts .................................................................................................. 9 1.4.8. Electrochemical challenges of oxygen electrocatalysts ................................................ 10 1.5. The aim of the thesis ............................................................................................................