(Invited) Engineering Local Chemical Environments in Electrolytes and at Electrode-Electrolyte Interface for Efficient Aqueous Batteries

Abstract

Electrolytes are an essential component of energy storage devices. Electrolyte composition has a significant impact on the environmental footprint, safety, price and performance of a battery. Aqueous electrolytes are non-flammable and can offer safer battery operation and lower toxicity. However, they suffer from a smaller electrochemical stability window compared to traditional organic electrolytes, which leads to lower energy density. To circumvent the small electrochemical stability window, highly concentrated “water-in-salt” (WIS) electrolytes, which demonstrate significantly wider stability window, were proposed and successfully applied to various aqueous energy storage systems including Li-ion and Zn metal batteries that are highly attractive for grid energy storage. However, since WIS electrolytes require large amounts of salt (often toxic) and have dramatically increased viscosity, it in turn limits their transport properties, charge-discharge rates, and usability in batteries.In this talk, the use of highly concentrated "water-in-salt" (WIS) electrolytes as a means of achieving increased charging efficiency and a wider stability window will be discussed in the context of aqueous Li-ion and Zn metal batteries. Further, we elaborate the role of cation solvation environment, electrolyte structure and hydrogen bonding on the physicochemical properties and electrochemical response of the system. We show that electrolyte composition affects the interfacial kinetics of Zn plating/stripping as well as the kinetics of the parasitic processes of electrolyte decomposition. Finally, we discuss how relatively dilute electrolytes can be engineered for efficient aqueous batteries. References Suo, O. Borodin, T. Gao, M. Olguin, J. Ho, X. Fan, C. Luo, C. Wang and K. Xu, Science, 2015, 350, 938Yamada, K. Usui, K. Sodeyama, S. Ko, Y. Tateyama and A. Yamada, Nat. Energy, 2016, 1, 16129R. Lukatskaya, J.I. Feldblyum, D.G. Mackanic, F. Lissel, D.L. Michels, Y. Cui, Z. Bao, Energy Environ. Sci., 2018, 11, 2876-2883 D.G. Vazquez, T. P. Pollard, J. Mars, J.M. Yoo, H.G. Steinrück, S. E. Bone, O. V. Safonova, M. F. Toney, O. Borodin, M.R. Lukatskaya, Energy Environ. Sci., 2023, DOI: 10.1039/D3EE00205E