Constructing Highly Ion‐Conductive Composite Solid Electrolytes via Crosslinking Strategy for Advanced Room‐Temperature Lithium Metal Battery

ABSTRACT Designing and developing solid‐state electrolytes (SSEs) with excellent comprehensive performance is currently a key challenge in high‐performance all‐solid‐state batteries. Herein, a novel composite solid polymer electrolyte is fabricated by embedding both Li 10 GeP 2 S 12 (LGPS) superionic conductors and cationic metal–organic frameworks (MOFs) in modified host poly(ethylene oxide) (PEO) utilizing mPEG‐silane coupling agent, which averts any phase separation between mPEG‐silane and PEO, enhances the polymers/fillers interface compatibility, and decreases the grain boundary resistance between all the particles, thus boosting the electrochemical properties of the SSEs. An exceptional room‐temperature Li + conductivity of 6.9 × 10 −4 S cm −1 , broad redox stability window of 5.36 V and high lithium‐ion transference number of 0.88 are obtained ascribed to the synergistic effect of polymer chains, LGPS and cationic MOFs. Accordingly, the Li symmetrical cell with the composite SSEs achieves an extremely long cycle stability of 11 000 h at 0.1 mA cm −2 . Additionally, the robust membrane structure and electrodes/SSEs interfacial compatibility enable the assembled LFP|Li solid battery to gain a discharge capacity of 130.7 mAh g −1 at 1 C over 1200 cycles. This work may open up a completely new path for the development of next‐generation high‐performance SSEs applied in the field of all‐solid‐state batteries.