A High-Filled Li₇La₃Zr₂O₁₂/Polypropylene Oxide Composite Solid Electrolyte with Improved Lithium-Ion Transport and Safety Performances for High-Voltage Li Batteries

The optimized combination of the organic/inorganic components in a composite solid electrolyte (CSE) plays a crucial role in improving its ion conductivity and thermal-mechanical performances. In this work, a high-filled Li7La3Zr2O12 (LLZO)/polypropylene oxide (PPO) CSE film was prepared by introducing LLZO microparticles in a flexible PPO polymer electrolyte. As the content of LLZO increases, the lithium-ion migration pattern is changed from migrating with the PPO chain segment movement to along the continuous fast ion conducting networks formed by the high-filled LLZO particles. When the LLZO content reaches 45 wt %, the room-temperature ion conductivity is up to 3.79 × 10–4 S cm–1, and the potential window is about 5 V. Meanwhile, the addition of LLZO particles enhances the mechanical and thermal properties of the PPO electrolyte, the maximum tensile strength reaches 56.41 Mpa, and the temperature resistance reaches above 200 °C. This CSE film with improved ion transport and safety performances shows high practical significance in the development of solid-state lithium batteries.