Al₂O₃ Fiber-Reinforced Polymer Solid Electrolyte Films with Excellent Lithium-Ion Transport Properties for High-Voltage Solid- State Lithium Batteries

Composite solid electrolytes (CSEs) with high ionic conductivity and good interfacial compatibility are the basis for the practical application of solid-state lithium batteries. The combination of suitable polymers and inorganic fillers is the key to the preparation of CSEs with excellent performance. In this work, a flexible-rigid composite solid electrolyte film was prepared by incorporating different weight ratios (5-20 wt %) of gamma-Al2O3 fibers into flexible polypropylene oxide (PPO) polymer electrolytes. Due to the addition of gamma-Al2O3 fibers, the ion migration path is shortened and the ion migration rate is effectively improved. At the same time, the Lewis acid groups of gamma-Al2O3 fibers react with TFSI- to release more Li+, which increases the number of lithium-ion migration. Therefore, when the content of gamma-Al2O3 fibers is 15 wt %, the room-temperature ionic conductivity reaches 3.38 x 10(-4) S cm(-1), the ion migration number is 0.70, and the electrochemical window is 5.6 V. In addition, lithiophilic gamma-Al2O3 reacts with Li metal to generate a Li-Al-O transition layer, which promotes Li+ interfacial transport and Li uniform deposition, and further inhibits the growth of Li dendrites. This Al2O3 fiber-reinforced CSE improves the lithium-ion transport properties and interface stability between lithium and the electrolyte and has positive practical applications in solid-state lithium batteries.