Electrochemically Oxidative Activation Inducing Ultrahigh Rate Capability of Vanadium Oxynitride/Carbon Cathode for Zinc-Ion Batteries.

As a promising candidate for large-scale energy storage, aqueous zinc-ion batteries (ZIBs) still lack cathode materials with large capacity and high rate capability. Herein, a spherical carbon-confined nanovanadium oxynitride with a polycrystalline feature (VNO/C) was synthesized by the solvothermal reaction and following nitridation treatment. As a cathode material for ZIBs, it is interesting that the electrochemical performance of the VNO/C cathode is greatly improved after the first charging process electrochemically oxidative activation. The oxidized VNO/C delivers a greatly enhanced reversible capacity of 556 mAh g at 0.2 A g compared to the first discharge capacity of 130 mAh g and a high capacity of 168 mAh g even at 80 A g. The characterizations verify that the insertion/extraction of Zn does not affect the crystal structure of oxidized VNO/C to promise a stable cycle life (retain 420 mAh g after 1000 cycles at 10 A g). The experimental analysis further elucidates that charging voltage and HO in the electrolyte are curial factors to activate VNO/C in that the oxygen replaces the partial nitrogen and creates abundant vacancies, inducing a conversion from VNO/C to VNO/C and then resulting in considerably strengthened rate performance and improved Zn storage capability. The study broadens the horizons of fast ion transport and is exceptionally desirable to expedite the application of high-rate ZIBs.