In Situ Electrochemically Activated Vanadium Oxide Cathode for Advanced Aqueous Zn-Ion Batteries.

The search for large-capacity and high-energy-density cathode materials for aqueous Zn-ion batteries is still challenging. Here, an in situ electrochemical activation strategy to boost the electrochemical activity of a carbon-confined vanadium trioxide (V 2 O 3 @C) microsphere cathode is demonstrated. Tunnel-structured V 2 O 3 undergoes a complete phase transition to a layered, amorphous, and oxygen-deficient Zn 0.4 V 2 O 5- m · n H 2 O on the first charge, thus allowing subsequent (de)intercalation of zinc cations on the basis of the latter structure, which can be regulated by the amount of H 2 O in the electrolyte. The electrode thus delivers excellent stability with a significantly high capacity of 602 mAh g -1 over 150 cycles upon being subjected to a low-current-rate cycling, as well as a high-energy density of 439.6 Wh kg -1 and extended life up to 10000 cycles with a 90.3% capacity retention. This strategy will be exceptionally desirable to achieve ultrafast Zn-ion storage with high capacity and energy density.