Sulfide-Based Flexible Solid Electrolyte Enhancing Cycling Performance of All-Solid-State Lithium Batteries

Research into all-solid-state lithium batteries (ASSLBs) is actively underway owing to their high energy density and enhanced safety features. To successfully advance the development of high-energy-density ASSLBs, manufacturing a thin and flexible solid electrolyte with both high ionic conductivity and mechanical strength is crucial. In this study, we present a sulfide-based (Li6PS5Cl, argyrodite) flexible solid electrolyte sheet utilizing poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) (EMG) terpolymer for ASSLB applications. This electrolyte exhibited a high ionic conductivity of 1.88 mS cm–1 at 60 °C and demonstrated good interfacial stability with lithium metal. The solid-state cell, comprising a Li–In anode, an EMG-based solid electrolyte sheet, and a LiNi0.9Co0.05Mn0.05O2 cathode, delivered a substantial discharge capacity of 229.2 mA h g–1 at 0.05 C and 60 °C, equivalent to a high areal capacity of 5.5 mA h cm–1. A comparative analysis with a cell assembled using a nitrile butadiene rubber-based solid electrolyte sheet revealed superior cycling performance in terms of cycling stability and high-rate performance.