A star-shaped polyimide covalent organic framework for high-voltage lithium-ion batteries

Abstract

Covalent organic frameworks are promising electrode materials for energy storage due to their uniform active sites, abundant pores, and high stability. However, the reported COF electrodes often display low discharge voltage, which limits their further applications. In this work, N,N,N,N-tetraphenylphenylenediamine (TPPDA) units were used to construct a novel polyimide COF, which exhibited a unique star-shaped structure. The COF material was used as the positive electrode for lithium-ion batteries and displayed a high discharge voltage up to 3.6 V, higher than those of almost all the COF electrode materials. The TPPDA units were demonstrated as redox active sites and exhibited two-electron redox processes, which exhibited the redox of TPPDA radical cations and the insertion/extraction of PF₆⁻ anions. This work offers a new strategy to design novel COF materials and develop high-voltage organic electrodes for energy storage.