Controllable Preparation And Optimization Of Zinc Storage Performance Of Vanadium-based Oxide Cathode Materials

In recent years,aqueous zinc-ion batteries(AZIBs)have attracted wide attention as a candidate to replace lithium-ion batteries(LIBs)due to the characteristics of low cost,safety,and environmental protection.To address the problems of AZIBs,such as low energy density and structural instability,Ce-doped vanadium pentoxide riched with oxygen vacancies and Ce-doped vanadium dioxide with high specific surface area as cathode materials of AZIBs were synthesized in this paper.The main contents are as follows:(1)We introduced oxygen vacancies while doping Ce ion into the V2O5 lattice by a simple one-step hydrothermal method(Od-Ce@V2O5)where a dual-effect design is adopted.In this method,it not only expands the layer spacing of layered V2O5,and stabilizes the structure,effectively inhibiting the positive electrode dissolution,but also greatly improves the electrical conductivity,which is favorable to improve the electrochemical performance.In addition,the REDOX process was dominated by the surface capacitance contribution,which is proved to be conducive to good rate performance and cycle stability.According to the electrochemical performance,a reversible capacity of 444 mAh g-1 at 0.5 A g-1 was obtained,and the energy density was 304.9 Wh kg-1.(2)On the basis of the above work,in order to further improve the cycling performance of vanadium-based cathode materials,we considered that the tunnel structure of VO2 is constructed by strong covalent bonds,which is more solid and stable than the layered structure connected by weak van der Waals forces,as well as the doping of exogenous elements can handle the problem of poor electrical conductivity of VO2.Thus,we synthesized Ce-doped VO2 with oxygen defects(Ce-VO2).Ce doping and the presence of oxygen vacancies change the local electron distribution of VO2 and improve the intrinsic conductivity.And Ce-VO2 has the nanoscale structure with the large specific surface area,effictively increasing the contact area between electrodes and electrolytes.As a result.the cathode still reserved the specific capacity of 158.5 mAh g-1 at the current density of 5 A g-1 after 1000 cycles.Besides,the Coulombic Efficiency also maintained about 100%.and it provided an excellent energy density of 312.8 Wh kg-1 at the power density of 142 W kg-1.