Ultrastable and High-Performance Zn/VO2 Battery Based on a Reversible Single-Phase Reaction

The aqueous zinc ion batteries (ZIBs) composed of inexpensive zinc anode and nontoxic aqueous electrolyte are attractive candidates for large-scale energy storage applications. However, their development is limited by cathode materials, which often deliver inferior rate capability and restricted cycle life. Herein, the VO2 nanorods show significant electrochemical performance when used as an intercalation cathode for aqueous ZIBs. Specifically, the VO2 nanorods display high initial capacity of 325.6 mAh g(-1) at 0.05 A g(-1), good rate capability, and excellent cycling stability of 5000 cycles at 3.0 A g(-1). Furthermore, the VO2 unit cell expands in a, b, and c directions sequentially during the discharge process and contracts back reversibly during the charge process, and the zinc storage mechanism is revealed to be a highly reversible single-phase reaction by operando techniques and corresponding qualitative analyses. Our work not only opens a new door to the practical application of VO2 in ZIB systems but also broadens the horizon in understanding the electrochemical behavior of rechargeable ZIBs.