High-Performance Polyimide Covalent Organic Frameworks for Lithium-Ion Batteries: Exceptional Stability and Capacity Retention at High Current Densities.

Organic polymers are considered promising candidates for next-generation green electrode materials in lithium-ion batteries (LIBs). However, achieving long cycling stability and capacity retention at high current densities remains a significant challenge due to weak structural stability and low conductivity. In this study, we report the synthesis of two novel polyimide covalent organic frameworks (PI-COFs), COF-JLU85 and COF-JLU86, by combining truxenone-based triamine and linear acid anhydride through polymerization. These PI-COFs feature layers with pore channels embedded with 18 carbonyl groups, facilitating rapid lithium-ion diffusion and enhancing structural stability under high current densities. Compared to previously reported organic polymer materials, COF-JLU86 demonstrates the excellent performance at high current densities, with an impressive specific capacity of 1161.1 mA h g at 0.1 A g, and outstanding cycling stability, retaining 1289.8 mA h g at 2 A g after 1500 cycles and 401.1 mA h g at 15 A g after 10000 cycles. Additionally, in situ infrared spectroscopy and density functional theory (DFT) calculations provide mechanistic insights, revealing that the high concentration of carbonyl redox-active sites and the optimized electronic structure contribute to the excellent electrochemical performance. These results highlight the potential of PI-COFs as high-performance organic electrode materials for LIBs, offering a promising solution to the challenges of long-term stability and capacity retention at high current densities.