Poly(propylene carbonate- co -thioether- co -ether) Terpolymer and Its Application as a Solid-State Electrolyte

Abstract Sulfur-containing polymers, especially those with sulfur in the main chain, have attracted significant interest owing to their diverse structures and unique properties, making them promising candidates for solid-state electrolytes. However, their controllable synthesis in metal-free catalysis remains challenging. Herein, a poly(propylene carbonate-co-thioether-co-ether) (PPCTE) terpolymer was synthesized by a one-step copolymerization of carbon dioxide (CO2), epoxides, and ethylene sulfide (ES) in a metal-free catalytic system. The PPCTE polymers with high-sulfur segments of 5% content in the main chain (PPCTE0.05) were obtained by regulating the monomer concentration ratio and the types of metal-free catalysts, yielding molecular weights of 27 kg mol–1. PPCTE0.05 exhibits a relatively low glass transition temperature of 5.8 °C, good thermal decomposition stability with 5% mass loss at 190 °C, and excellent flexibility of 647% elongation at break. Notably, the PPCTE0.05-based solid-state polymer electrolyte achieves a low impedance of 99 Ω, high ionic conductivities (5.36 × 10–5 S cm–1 at room temperature, 1.77 × 10–4 S cm–1 at 60 °C), a low activation energy of 0.29 eV, and a wide electrochemical window of 5.21 V. This work establishes a simple, economical, and eco-friendly synthetic route for main-chain sulfur-containing polymers and offers a valuable reference for designing solid-state polymer electrolytes.