Achieving high performance in aqueous iron-ion batteries using tunnel-like VO 2 as a cathode material.

The research on aqueous iron-ion batteries (AIIBs) is still in its early stages and highly limited by the lack of suitable cathode materials. In this study, we propose using tunnel-like VO 2 as a cathode material, which delivers a high capacity of 198 mA h g -1 at 0.2 A g -1 . Besides, the AIIB exhibits appreciable cycling performance, retaining 78.9% of its initial capacity after 200 cycles. The unique structure of VO 2 and the multiple valence states of vanadium in VO 2 enable the reversible storage of Fe 2+ during cycling. This work presents a new choice for the cathode and considerable development prospects in AIIBs.