Dual-active centers of porous triazine frameworks for efficient Li storage

Abstract

Integrating n-type and p-type redox-active centers into porous frameworks is an efficient approach to simultaneously mitigate the intrinsic problems of poor utility, low output voltage, and sluggish kinetics of organic electrodes for lithium ion batteries (LIBs). However, it is challenging to achieve an optimal utilization of the well-defined ordered porous structure and the multiple active centers due to the stacking structure of conventional covalent organic frameworks. Herein, we develop a post-modification approach to synthesize a bipolar pyrene-4,5,9,10-tetraone based porous covalent triazine frameworks (CTFs) for efficient dual-ion storage. The post-modification method successfully protects the active carbonyl groups under harsh conditions and effectively exposes the redox centers. The amorphous phase dominated CTFs enables excellent Li+ diffusion and high utilization of active sites, leading to ultrahigh specific capacity of 351 mAh/g at 0.2 A/g and impressive stability for 3000 cycles at 5.0 A/g. Moreover, the efficient dual-ion storage mechanism was confirmed by the in-depth investigation with ex situ FT-IR, and XPS study. Theoretical calculations also unveil the unique energy storage pathway using both p-doped and n-doped states for the intercalation of anions and cations. This work highlights the significance of the integrating strategy which allows the combination of dual-active-center with conjugated porous structure, broadening the avenues of organic electrode materials towards high-performance LIBs.