Application of Covalent Organic Frameworks in High-performance Lithium-ion Battery Anode Materials

In this work, two covalent organic frameworks(COF-1, COF-2) with high thermal stability, good crystallinity, and large specific surface area were prepared through polycondensation. When used as anode materials for lithium-ion batteries(LIBs), they exhibited high reversible capacities(charging specific capacities after 150 cycles, COF-1: 484 mA center dot h/g and COF-2: 327 mA center dot h/g, respectively), excellent rate performance(reversible capacities at 2 and 10 A/g current densities, COF-1: 296, 180 mA center dot h/g, and COF-2: 265, 166 mA center dot h/g, respectively) , working capacity under extremely high current density(charging specific capacities for 2000 cycles of 5 A/g current density, COF-1: 572 mA center dot h/g, COF-2: 332 mA center dot h/g) and operating performance under extreme temperatures(charging specific capacities after 40 cycles in 50 and -15 degrees C environments, COF-1: 2101, 218 mA center dot h/g, COF-2: 1760, 172 mA center dot h/g). In addition, both types of COFs have the ability to activate electrochemical active groups as charging and discharging continue. COF-1 and COF-2 were cycled 400 times without adding conductive agents, and the charging specific capacity increases from 23 and 16 mA center dot h/g to 45 and 31 mA center dot h/g, respectively. And through the analysis of experimental data, we prove that under the conditions of high current density or high temperature environment, which can accelerate the ion diffusion rate, the activation effect is more favorable. By comparing these two types of COF materials, we also found that COF-1 with triazine ring structures has better lithium storage performance and electrochemical reaction kinetics than COF-2 with all benzene ring structures, indicating that C=N in the aromatic ring may be a group with high electrochemical activity.