Boosting the zinc ion storage capacity and cycling stability of interlayer-expanded vanadium disulfide through in-situ electrochemical oxidation strategy

Metallic vanadium dichalcogenides with high conductivity and large layer spacing are fantastically potential to be cathode candidates for aqueous zinc ion batteries. However, simply reliance on the reversible Zn2+ intercalation/deintercalation process in the layer structure of vanadium dichalcogenides makes it suffer from low specific capacity and limited cycling number. Here we report a facile in-situ electrochemical oxidation strategy to boost the zinc ion storage capacity of interlayer-expanded vanadium disulfide (VS2·NH3) hollow spheres with satisfying cyclic stability. The hydrated vanadium oxide (V2O5·nH2O) generated from oxidized VS2·NH3, are endowed with reduced nanosheet size and subordinated porous structure, which provides abundant accessible sites and accelerates the zinc ion diffusion process. As a result, the VS2·NH3 derived cathode after the electrochemical oxidation process delivers a high reversible capacity of 392 mA h g-1 at 0.1 A g-1 and long cyclic stability (110% capacity retention at 3 A g-1 after 2000 cycles). The efficient oxidation process of VS2·NH3 cathode and the storage mechanism in the subsequent cycles are schematically investigated. This work not only reveals the zinc ion storage mechanism of the oxidized VS2·NH3 but also sheds light on advanced design for high-performance Zn ion cathode materials.