Aluminum Oxide Membrane Regulating the Performance of PEO Based Electrolyte for High-Performance Quasi-Solid-State Lithium Batteries

Solid electrolyte materials have improved the safety and stability of quasi-solid-state lithium-ion batteries, making them highly desirable. Through mesoporous confinement regulation of anodic aluminum oxide (AAO) membranes and optimization of lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) concentration, a low-crystallinity polyethylene oxide (PEO) based solid electrolyte membrane, 18PEO/LiTFSI-160, was prepared. This electrolyte shows that when the molar ratio of ethylene oxide to lithium ion (EO: Li) is 18 and the AAO pore size is 160–200 nm, the electrolyte membrane exhibits a crystallinity as low as 13%, a room-temperature ionic conductivity of 9.78 × 10⁻⁵ S cm⁻¹, a Li⁺ transference number increased to 0.4, and an electrochemical window broadened to 5.1 V. In Li/Li symmetric cell tests, the interfacial impedance remained stable at 180 Ω after 160 h of cycling, with a smooth interface and no dendrite formation observed. Full-cell performance tests further verified the optimization effects: the cell assembled with LiFePO₄ delivered a discharge capacity of 142 mAh/g at a 0.1 C rate and retained 95% of its capacity after 100 cycles. The 18PEO/LiTFSI-160 solid polymer electrolyte demonstrates promising performance and is a viable material for all-solid-state lithium metal secondary batteries. The AAO membrane plays a crucial role in enhancing its performance.