Self‐Transformation Strategy Toward Vanadium Dioxide Cathode For Advanced Aqueous Zinc Batteries

In the lithium-dominated era, rechargeable Zn batteries are emerging as a competitive alternative. However, the sluggish kinetics of ion diffusion and structural destruction of cathode materials have thus far hampered the realization of future large-scale energy storage. Herein, an in situ self-transformation approach is reported to electrochemically boost the activity of a high-temperature, argon-treated VO2 (AVO) microsphere for effective Zn ion storage. The presynthesized AVO with hierarchical structure and high crystallinity allows efficient electrochemical oxidation and water insertion to induce self-phase transformation into V2 O5 ·nH2 O within the first charging process, which leads to rich active sites and fast electrochemical kinetics. Using AVO cathode, an outstanding discharge capacity of 446 mAh g-1 at 0.1 A g-1 , high rate capability of 323 mAh g-1 at 10 A g-1 and excellent cycling stability for 4000 cycles at 20 A g-1 with high capacity retention are demonstrated. Importantly, such zinc-ion batteries with phase self-transition can also perform well at high-loading, sub-zero temperature, or pouch cell conditions for practical application. This work not only paves a new route to design in situ self-transformation in energy storage devices, but also broadens the horizons of aqueous zinc-supplied cathodes.