Electron structure and defect co-modulation to boost zinc storage performance of urchin-like VS4-based microspheres as advanced cathodes for aqueous Zn-ion batteries

Recently, aqueous zinc ion batteries (AZIBs) have been widely favored for their intrinsic safety, low cost and environmental friendliness; however, the vast volume expansion, poor electrical conductivity and low-density zinc insertion and extraction channels of the cathodes cannot meet the requirements of practical application for AZIBs. Herein, urchin-like Co-doped VS4 microspheres (Co-VS4-δ-x) with the co-regulation of electron structure and defect have been developed and synthesized by a one-step solvothermal procedure as an advanced cathode material for AZIBs. The introduction of active multivalent Co ions achieves the interfacial charge rearrangement of Co-VS4-δ-x electrode and the widening of the layer spacing to reduce the transfer resistance and interfacial attraction of Zn2+ between the layers. Moreover, the formation of sulfur defects shortens the Zn2+ transport distance and enhances the electrical conductivity and electrochemical kinetics of Co-VS4-δ-x material. In addition, the urchin-like micromorphology of the material dramatically increases the contact area between electrolyte and electrode material and the active sites of electrochemical reaction. Based on the above advantages, the zinc storage performance of Co-VS4-δ-x has been greatly enhanced, delivering the specific capacities of 306.4 mAh g−1 and 270.7 mAh g−1 at 0.5A g−1 and 5A g−1, respectively, and exhibiting excellent cycling stability with the capacity retention of 87.0% after 3000 cycles at 5 A g−1. This investigation proposes an effective strategy to develop high-performance vanadium-based cathodes for AZIBs by charge rearrangement, defect modulation and morphology optimization.