Boosting Aluminum Storage in Highly Stable Covalent Organic Frameworks with Abundant Accessible Carbonyl Groups

Abstract

Aluminum batteries employing organic electrode materials present an appealing avenue for sustainable and large-scale energy storage. Nevertheless, conventional organic materials encounter limitations due to their restricted active sites, known instability, and sluggish redox kinetics. In this study, a redox-active covalent organic framework supported by CNT is reported, enriched with substantial C═O groups, as an advanced cathode material for Al-organic batteries. Theoretical simulation and ex situ analysis unveil the pivotal roles of C═O groups in effectively storing AlCl2+. As a result, Al batteries with the organic cathode exhibit a specific capacity of 290 mAh g−1 at 0.2 A g−1 and outstanding rate performance. Furthermore, it retains a reversible capacity of 170 mAh g−1 even after 32 000 cycles at 10 A g−1 and attains an energy density of 389 Wh kg−1. The remarkable performance stems not only from the abundant C═O and C─N groups enabling the storage of multiple AlCl2+ by the favorable pseudocapacitive process, but also from the synergistic interplay between the robust COF network and the conductive CNT channels that significantly enhances structural stability and accelerates ion/electron diffusion. This work stands to inspire further research in the pursuit of stable organic cathodes, fostering designs with plentiful accessible redox-active sites to boost energy storage capabilities.