Tailoring the interaction of covalent organic framework with the polyether matrix toward high‐performance solid‐state lithium metal batteries

Abstract Solid polymer electrolyte is one of the most promising avenues to construct next‐generation energy storage systems with high energy density, high safety, and flexibility, yet the low ionic conductivity at room temperature and poor high‐voltage tolerance have limited their practical applications. To address the above issues, we design and synthesize a highly crystalline, vinyl‐functionalized covalent organic framework (V‐COF) rationally grafted with ether‐based segments through solvent‐free in situ polymerization. V‐COF can afford a fast Li+ conduction highway along the one‐dimensional nanochannels and improve the high‐voltage stability of ether‐based electrolytes due to the rigid and electrochemically stable networks. The as‐formed solid‐state electrolyte membranes demonstrate a superior ionic conductivity of 1.1 × 10−4 S cm−1 at 40°C, enhanced wide electrochemical window up to 5.0 V, and high Young's modulus of 92 MPa. The Li symmetric cell demonstrates ultralong stable cycling over 600 h at a current density of 0.1 mA cm−2 (40°C). The assembled solid‐state Li|LiFePO4 cells show a superior initial specific capacity of 136 mAh g−1 at 1 C (1 C = 170 mA g−1) and a high capacity retention rate of 84% after 300 cycles. This study provides a novel and scalable approach toward high‐performance solid ether‐based lithium metal batteries.