Aluminum Oxide Membrane Regulating the Performance of <scp>PEO</scp> Based Electrolyte for High‐Performance Quasi‐Solid‐State Lithium Batteries

ABSTRACT 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 LiFePO 4 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.