Ionogel hybrid polymer electrolytes encompassing room-temperature ionic liquids for 4V-class Li-metal batteries operating at ambient temperature

Abstract

ABSTRACTIn this study, we prepare ionogels composed of bisphenol A ethoxylate dimethacrylate, poly(ethylene glycol) methyl ether methacrylate, lithium bis(trifluoromethanesulfonyl)imide, and 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide or 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide ionic liquids via rapid, scalable, solvent-free UV-induced polymerization. The various hybrid polymer electrolyte formulations are thoroughly characterized using a comprehensive set of physico-chemical and electrochemical methods, including gel content, FTIR, rheology, DTMA, TGA, SEM, cycling voltammetry, impedance spectroscopy, and galvanostatic cycling in laboratory-scale Li-metal cells. We particularly focus on the influence of using two different ionic liquids as reaction medium on the properties of the resulting materials and their electrochemical behaviors. Our results indicate that viscosity affects the polymerization kinetics of the ionogels, which in turn might affect their thermal stability and galvanostatic cycling behavior. In the purpose of promoting overall performance of solid-state batteries, we also present the results of composite electrolytes obtained by introducing Li7La3Zr2O12 (LLZO) into ionogels and following in-situ UV-polymerisation. The addition of LLZO ceramic results in more porous solid networks, leading to enhanced charge/discharge stability at ambient temperature and higher C-rates featuring 4V-class NMC cathodes, enlightening the promising prospects of the developed materials to be successfully implemented as stable, durable, and efficient electrolytes in next-generation Li-metal cells.

Keywords

• Ionogel
• room temperature ionic liquid
• polymer electrolyte
• composite polymer electrolyte
• garnet ion conductor
• lithium metal battery