Surface Modification Of Two Vanadium Oxides-based Cathode Materials And Performance Study In Zinc-ion Battery

In recent years,secondary batteries mainly based on lithium-ion batteries have been widely used in new energy vehicles,consumer electronics,energy storage power stations and other fields.However,the lack of key resources in lithium-ion batteries and the poor safety of organic electrolytes are prone to safety risks,prompting people to turn their attention to safer and cheaper energy storage systems.aqueous zinc ion battery（AZIBs）is highly recommended for compatibility of zinc metal with aqueous electrolyte.The cathode materials of aqueous zinc ion battery are rich and varied,the modification of cathode materials seems to provide more possibilities effectively improve the electrochemical performance of aqueous zinc ion battery.Therefore,in this paper,the vanadium oxide compounds obtained by adding different reagents with ammonium vanadate as raw material are taken as the research object,and the surface modification was carried on them Then,their electrochemical performance and energy storage mechanism were studied respectively.The main research contents of this paper are as follows:Firstly,（NH₄）₂V₆O₁₆·1.4H₂O and（NH₄）₂V₆O₁₆·0.9H₂O@RGO cathode material with nano-belt morphology were synthesized by hydrothermal method and assembled with zinc foil as the anode to form a zinc-ion battery.The electrochemical performance of（NH₄）₂V₆O₁₆·0.9H₂O modified with reduced graphene is better than that of（NH₄）₂V₆O₁₆·1.4H₂O:The discharge specific capacity can up to 500 m Ah/g at 0.1 A/g,at a current density of 5A/g,the specific discharge capacity can still maintain 322 m Ah/g after 1000 cycles,and the corresponding capacity retention rate is 92.8%.This is attributed to the fact that graphene coated on the surface of（NH₄）₂V₆O₁₆·0.9H₂O@RGO nanobelts can stabilize the structure during zinc ion（de）-intercalation and improve the conductivity of the electrode material.Secondly,V₂O₃ cubic particles were synthesized by simple solvothermal method,and the size of V₂O₃ particles was reduced from micron to nanometer by ball milling.The contact area between ball-milling V₂O₃ electrode and electrolyte increases and the active sites increase,which enhances the ion transfer rate of electrode.The ball-milled V₂O₃ exhibits better rate performance and cycling performance than the original V₂O₃:At a current density of 10 A/g,the specific discharge capacity can still maintain 212 m Ah/g after 1000 cycles,and the corresponding capacity retention rate is 100%.When the power density is 13954 W/kg,the energy density can still remain at 139 Wh/kg.With tha aid of high resolution transmission electron microscopy（HRTEM）and EPR analysis,it is found that The V₂O₃ phase is converted to the VO_2-X phase with oxygen defect after charging to 1.6 V.