(Invited) Temperature-Flexible High Performance Quasi Solid-State Batteries

Abstract

Lithium-rich garnet solid electrolytes are one of the most promising avenues for high temperature lithium metal batteries due to the non-flammability, high ionic conductivity, and exceptional thermal stability compared to liquid electrolytes. One of the main issues remaining is the interface of garnet with cathode materials. Simply layering the garnet and cathode results in high interfacial impedance [1] , whereas co-sintering studies attempting to improve contact have shown detrimental reactions [2],[3] . Organic or ionic liquid electrolytes have been applied to wet the interface with traditionally cast cathodes and have shown improvement in room temperature performance [1] ,[4] . In this study, the ionic liquid electrolyte (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide with LiTFSI was utilized as catholyte due to its inherent high thermal stability >100°C and nonvolatility to produce cells capable of both room temperature and high temperature cycling. The catholyte was applied in garnet-based batteries with a lithium metal anode and either LiFePO4 or TiS2 cathodes. The cell performance and solid-liquid electrolyte interface were studied from room temperature into the high (> 90°C) temperature regime. High utilization of cathodes, high rate capability, and impressive cycling stability were observed during high temperature cycling. Using tools such as electrochemical impedance spectroscopy, distribution of relaxation times analysis, and electron microscopy, the role of interfacial layers was elucidated to understand and optimize the system. This dual electrolyte approach shows thermal flexibility from room temperature to beyond the boiling point of many common liquid electrolytes. [1] Frederic Aguesse and others, ‘Investigating the Dendritic Growth during Full Cell Cycling of Garnet Electrolyte in Direct Contact with Li Metal’, 2017 <https://doi.org/10.1021/acsami.6b13925>. [2] V Thangadurai and W Weppner, ‘Investigations on Electrical Conductivity and Chemical Compatibility between Fast Lithium Ion Conducting Garnet-like Li 6 BaLa 2 Ta 2 O 12 and Lithium Battery Cathodes’, 142 (2005), 339–44 <https://doi.org/10.1016/j.jpowsour.2004.11.001>. [3] Lincoln J Miara and others, ‘First-Principles Studies on Cation Dopants and Electrolyte | Cathode Interphases for Lithium Garnets’, 2015 <https://doi.org/10.1021/acs.chemmater.5b01023>. [4] Manuel Weiss and others, ‘From Liquid - to Solid - State Batteries : Ion Transfer Kinetics of Heteroionic Interfaces’, Electrochemical Energy Reviews, 2020 <https://doi.org/10.1007/s41918-020-00062-7>.