Functionalization of Defective Covalent Organic Frameworks for High‐Performance Solid‐State Electrolytes

Covalent organic frameworks (COFs) exhibit outstanding structural tunability, clearly defined ion pathways, and remarkable thermal/chemical stabilities, rendering them highly promising candidates for applications in solid-state electrolytes. However, it remains a challenge to develop a versatile method to incorporate both ionic groups and electron-withdrawing units into a single framework for effectively improving the lithium-ion conductivity. Herein, a series of novel [3+3] defective COFs is successfully synthesized featuring active amine/aldehyde anchoring sites for subsequent post-modification, and regulates the ion conductivity through elaborately tuning the anionic/cationic groups and weak/strong electron-withdrawing units. As a result, COF-ECJTU1-60-SO₃Li-based solid-state electrolytes demonstrate lithium-ion conductivity (1.30 × 10^-5 S cm^-1) and a remarkably high t_Li+ (0.87) at 303 K. In addition, Li/COF-ECJTU1-60-SO₃Li/LiFePO₄ solid lithium-ion battery demonstrates an initial charge capacity of 145.7 mAh g^-1 at a rate of 0.2 C, maintaining 92.71% capacity retention with a coulombic efficiency of 98.5% after 100 cycles under 353 K. This work not only presents a new approach for constructing functional COFs, but also systematically explores the synergistic interaction between ionic groups and electron-withdrawing units, thereby enabling the development of high-performance solid-state electrolytes.