Two-Dimensional Covalent Organic Frameworks with Enhanced Aluminum Storage Properties

Aluminum-ion batteries (AIBs) are regarded as one of the most promising types of energy storage device in light of the safety, natural abundance, and electrochemical properties of aluminum. However, the rate capabilities of AIBs are limited owing to the sluggish kinetics of chloroaluminate anions. In this study, a covalent organic framework (COF) is adopted as the cathode material in AIBs. Theoretical and experimental results suggest that the COFs allow fast anion diffusion and intercalation without structure collapse, owing to the robust frameworks and the hierarchical pores with a large specific surface area of 1794 m²  g^-1 . The resultant AIB exhibits remarkable long-term stability, with a reversible discharge capacity of 150 mAh g^-1 after 13 000 cycles at 2 A g^-1 . It also shows an excellent rate capability of 113 mAh g^-1 at 5 A g^-1 . This work fully demonstrates the potential of COFs in the storage of chloroaluminate anions and other large-sized ions.