Low melting non-corrosive asymmetric thioether-TFSI Li salts for solid polymer electrolytes

Abstract

High crystallinity in PEO-based solid polymer electrolytes limits ion transport and stability in Li-metal batteries. Two asymmetric, low-melting thioether-TFSI Li salts were synthesized via a thiol–ene route and incorporated into PEO. They suppress crystallinity while maintaining conductivity and electrochemical performance, and reduce Al corrosion via stable passivation layer formation. The resulting SPEs have improved Li compatibility and enable stable Li||LiFePO₄ cells cycling with high capacity retention and coulombic efficiency.