Cross-Linked Polypropylene Oxide Solid Electrolyte Film with Enhanced Mechanical, Thermal, and Electrochemical Properties via Additive Modification

Benefiting from the flexibility and low cost, polymer electrolytes are widely used in ultra-thin solid lithium-ion batteries. However, low room-temperature ion conductivity and poor mechanical and thermal stability are key defects hindering the wide application of the polymer solid-state electrolyte. In this work, a cross-linked polypropylene oxide (PPO) polymer solid electrolyte film with excellent mechanical, thermal and electrochemical properties was prepared by introducing the cellulose skeleton, polyglycol (peg400), and zirconia (ZrO2) additives. The cellulose skeleton and peg400 enhance the flexibility, tensile strength and thermal stability(>200 °C) of the electrolyte film, while ZrO2 promotes the movement of polymer segments and the dissociation of lithium salts to improve the ionic conductivity (6.67 × 10–4 S cm–1 at room temperature) and increase the potential window (>4.6 V vs Li/Li+) of the electrolyte. This composite electrolyte film can be used in LiFePO4(LFP) and LiNi0.6Co0.2Mn0.2 (NCM622) solid-state batteries and shows good cycling stability with 600 cycles for LFP. This rigid-flexible composite solid electrolyte film with high ion conductivity and good mechanical and thermal properties has good prospects for application in solid-state Li batteries.