Amorphous Bimetallic Oxides Fe-V-O with Tunable Compositions toward Rechargeable Zn-Ion Batteries with Excellent Low-Temperature Performance.

Vanadium oxides have been considered as promising cathode candidates for zinc-ion batteries (ZIBs) because of their high theoretical specific capacity. However, the poor rate performance and the unsatisfactory cycle life resulting from the sluggish electrode kinetics seriously impede their practical implementation. Herein, we report the rational design of amorphous Fe-V-O bimetallic oxides with tunable compositions as cathodes for aqueous ZIBs. The bimetallic Fe-V-O oxides show improved composition-dependent Zn storage performance and superior structural integrity during cycling. The enhanced electrode kinetics is attributed to the superior electronic conductivity of Fe-V-O oxides than pristine VO owing to the introduction of the Fe element and an amorphous crystalline structure, which can provide reduced diffusion paths and more free volume for Zn insertion. As a result, the as-prepared Fe-V-O exhibits outstanding rate capability and impressive cycling stability. Particularly, a stable reversible capacity of 70 mA h g can be still maintained after 2500 cycles at 5 A g, corresponding to the high capacity retention of 95%.