Solid polymer electrolyte membrane based on cationic polynorbornenes with pending imidazolium functional groups for all‐solid‐state lithium‐ion batteries

Abstract

AbstractSolid polymer electrolytes (SPEs) have received extensive attention in the realm of lithium‐ion batteries due to their safety performance, higher specific capacity and structural designability. In recent years, poly ionic liquids (PILs) have been attracting the attention of many researchers because of their high ionic conductivity, wide electrochemical stability window, high thermal stability and less‐flammability in comparison with common liquid electrolytes. We selected imidazole cations as functional groups to be attached to the side chain of the polymer to prepare bis‐imidazole functionalized benzo‐norbornadiene monomer, which copolymerized with epoxy‐functionalized norbornene monomer and norbornene (NB) monomer to obtain triblock copolymer. The prepared triblock copolymer was blended with lithium salt (LiTFSI) to obtain a solid polymer electrolyte membrane (SPEM). SPEM achieved an excellent ionic conductivity of 3.1 × 10−5 S cm−1 at 30°C, exhibited an electrochemical stability window of up to 4.3 V versus Li/Li+ (25°C) and thermal stability up to 275°C under protective (N2) atmosphere. The NCM811/SPEM/Li batteries have exhibited a first discharging capacity of 149.1 mAh g−1 at 0.1 C‐rate and the discharge capacity kept 141.6 mAh g−1 at 0.2 C‐rate after 50 charge and discharge cycles at 30°C.