Linkage engineering regulated π-conjugated covalent organic framework (COF)-based anodes for high-performance LIBs

Abstract

COFs have garnered widespread attention and demonstrated significant potential in energy storage and conversion, attributed to their predesigned structures, high surface areas, and excellent stability. However, designing and preparing COFs with high-performance Li-ion storage capabilities among different types of linkages remains challenging. In this work, we synthesized two types of COFs with distinct linkages through linkage engineering. COFs@BOA, incorporating oxazole linkages, and COFs@IM, incorporating imine linkages, both exhibited fine crystallinity and stability. Due to the semiconductor properties of the COFs, we employed an in situ growth approach to deposit the COFs onto the surface of carbon nanotubes. The resulting COFs@BOA-30 and COFs@IM-30 composites demonstrated highly reversible capacity, with the latter exhibiting a superior capacity of up to 1100.3 mA h g⁻¹ at 100 mA g⁻¹. The capacity contribution of COFs@IM was calculated to be 1696.0 mA h g⁻¹ in the COFs@IM-30 composite, while COFs@BOA contributed only 925.8 mA h g⁻¹. DFT calculations suggest that the discrepancy in capacities may be attributed to the lower LUMO–HOMO gap of COFs@IM. Additionally, electrical conductivity measurements indicate that COFs@IM has better conductivity than COFs@BOA, highlighting the superior performance of COFs@IM. This study underscores the significance of linkage engineering in designing COFs to improve the performance of organic electrodes in LIBs.