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

Abstract 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‐SO ₃ Li‐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‐SO ₃ Li/LiFePO ₄ 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.