Fabrication And Electrochemical Performance Of Vanadium-based Compounds

The increasing demand for the green and renewable energy resource urgently requires highly efficient electrochemical energy storage equipment.The fabrication and structural optimization of high-performance electrode materials determines the electrochemical performance of secondary batteries.Among numerous electrode materials,vanadium-based compounds possess variable element valences and diverse crystalline structures,and are deemed as the promising electrode material.Yet the inferior intrinsic electronic conductivity and slower ion diffusion ability of vanadium-based materials,hinder their further application in the field of secondary batteries.In this paper,the strategies of structural regulation and compositing with high-conductive materials are applied to prepare the V₃S₄/r GO composites and interlayer-expanded（NH₄）_xV₄O₁₀nanoflower.Moreover,the Li-storage and Zn-storage performance of the two samples was also carefully investigated,respectively.The main investigation contents and results are as follows:（1）The hierarchical V₃S₄/r GO composites were successfully fabricated by freeze-drying and high-temperature sulfidation treatment.The hierarchical structure of 1D V₃S₄ nanowires embedded in r GO nanosheets can facilitate ion/electron diffusion on 2D planes.The wrinkle r GO nanosheets are able to prevent the agglomeration of V₃S₄ and mitigate the volume variation during periodic charging/discharging.Therefore,the VG-70 electrode displays an average capacity of 770 m A h g^-1 at 0.1 A g^-1,and maintains stable cycling over 1000 cycles with a specific capacity of589 m A h g^-1 at 1.0 A g^-1.（2）A simple one-step hydrothermal method was adopted to synthesize ammonium vanadate hydrate with different interlayer spacing.By adjusting the p H value of the solution,the NH₄⁺content in V₄O₁₀interlayer can be effectively decreased,realizing the（001）crystalline plane spacing expanded from 9.4（?）to 11.9（?）,therefore the NH₄⁺-deficient（NH₄）_xV₄O₁₀ was fabricated successfully.The unique structure is beneficial for rapid Zn²⁺diffusion and can ensure the structural stability upon periodic intercalation and deintercalation process.The nanosheet-assembled 3D nanoflower can effectively shorten the ion transportation paths,and the internal pores derived from the interconnected nanosheets are conducive to electrolyte penetration.Therefore,the（NH₄）_xV₄O₁₀cathode can realize stable cycling of 1000 cycles with capacity retention of78.9%at current density of 5.0 A g^-1.