Self-degrading functional unit introduction for anti-oxidation ability enhancement of a poly(vinyl ethylene carbonate) electrolyte

Abstract

Poly(vinyl ethylene carbonate) (PVEC) electrolyte is a promising option for high-performance solid-state lithium metal batteries (SSLMBs). However, its anti-oxidation ability is still too low to match high-voltage cathode materials. Herein, a novel copolymer electrolyte, poly(vinyl ethylene carbonate-3-sulfolene) (P(VEC-SF)-PE) has been developed by copolymerizing 3-sulfolene (SF) and vinyl ethylene carbonate (VEC) monomer precursors. The P(VEC-SF)-PE possesses a wide electrochemical stability window of 5 V (vs. Li⁺/Li), high lithium ion transference number of 0.6 and ionic conductivity of 7.97 × 10⁻⁴ S cm⁻¹ at 25 °C. The anti-oxidation ability is enhanced by the pre-degradation of sulfolene-based functional units and confirmed by multiple techniques. The P(VEC-SF)-PE based SSLMBs with the LiCoO₂ cathode exhibit a high discharge capacity and good rate performances when charged to 4.5 V. This study presents an efficient strategy to improve the compatibility of the cathode/electrolyte interface and the electrochemical performances of high-energy SSLMBs.