MIL-100(V) derived porous vanadium oxide/carbon microspheres with oxygen defects and intercalated water molecules as high-performance cathode for aqueous zinc ion battery

The development of aqueous zinc ion battery cathode materials with high capacity and high magnification is still a challenge. Herein, porous vanadium oxide/carbon (p-VOx@C, mainly VO2 with a small amount of V2O3) core/shell microspheres with oxygen vacancies are facilely fabricated by using a vanadium-based metal–organic framework (MIL-100(V)) as a sacrificial template. This unique structure can improve the conductivity of the VOx, accelerate electrolyte diffusion, and suppress structural collapse during circulation. Subsequently, H2O molecules are introduced into the interlayer of VOx through a highly efficient in-situ electrochemical activation process, facilitating the intercalation and diffusion of zinc ions. After the activation, an optimal sample exhibits a high specific capacity of 464.3 mA h g−1 at 0.2 A g−1 and 395.2 mA h g−1 at 10 A g−1, indicating excellent rate performance. Moreover, the optimal sample maintains a capacity retention of about 89.3% after 2500 cycles at 10 A g−1. Density functional theory calculation demonstrates that the presence of oxygen vacancies and intercalated water molecules can significantly reduce the diffusion barrier for zinc ions. In addition, it is proved that the storage of zinc ions in the cathode is achieved by reversible intercalation/extraction during the charge and discharge process through various ex-situ analysis technologies. This work demonstrates that the p-VOx@C has great potential for applications in aqueous ZIBs after electrochemical activation.