Preparation And Electrochemical Performance Of Zn₃V₂O₈ Composite Anode Material

As the main component of batteries,how to improve the electrochemical performance of the anode materials has always been the primary problem that researchers solve.Ternary mixed transition metal oxides(Mixed transition-metal oxides MTMO)have attracted much attention due to their diversity,structural flexibility,and synergistic effects originating from multiple metals.Among them,Zn3V2O8 has been gradually studied as a substitute for traditional lithium-ion negative electrode materials due to its simple synthesis method,wide source of raw materials,no heavy metal pollution environment,and considerable theoretical specific capacity.However,it also has some inherent problems such as low electronic conductivity,During the charging and discharging process,the massive volume expansion generated by the conversion reaction leads to material pulverization and deactivation.These undeniable issues greatly limit the practical application of Zn3V2O8.In response to the above issues,this article explores morphology modification,material composition,surface coating,and other aspects.Through material physical and electrochemical characterization,the reaction mechanism of Zn3V2O8 negative electrode material charge and discharge and how to improve its electrochemical performance are explored.As the volume change is one of the main reasons for the capacity attenuation of MTMO anode material,Zn3V2O8 nanosheet structure was prepared by reflux method.SEM test showed that the Zn3V2O8 pure phase material prepared by reflux method was formed by the agglomeration of nano-sheets.The electrochemical performance test showed that the specific discharge capacity of Zn3V2O8 was 296.2 mAh g-1 after 100 turns at the current density of 0.2 A g-1.The cyclic stability of pure phase materials is poor,which may be related to the agglomeration phenomenon.Multi-walled carbon nanotubes(MWCNTs)were introduced in the preparation process of Zn3V2O8 by reflow method in order to inhibit the severe agglomeration of materials and enhance their electrical conductivity.SEM and TEM tests showed that the composite was composed of Zn3V2O8 hierarchical microspheres with a cross-linked structure formed by CNTs,and the distribution of the composite was uniform.The agglomeration phenomenon is greatly reduced,and the results of electrochemical performance test show that ZVO/CNTs-25 sample can reach the reversible specific capacity of 1039.6/1049.5 mAh g-1 after 100 cycles at 0.2 A g-1 current density,even at 5.0 A g-1 current density.ZVO/CNTs-25 samples could still provide 365.6 mAh g-1 discharge capacity after 500 cycles.Meanwhile,electrochemical impedance tests showed that ZVO/CNTs-25 samples had the lowest electrochemical impedance and the highest lithium ion diffusion coefficient.In order to further improve the reversible specific capacity of Zn3V2O8,we firstly synthesized Zn3V2O8 nanoparticles by coprecipitation method and then synthesized ZVO@CeO2 composite by solvent evaporation method.Ce4+in CeO2 can preferentially react with hydrogen fluoride to eliminate the corrosion of hydrogen fluoride on the electrolyte and improve the electrochemical performance of the material.The ZVO@CeO2-3 sample has the best electrochemical performance when the recombination ratio is 3%.The discharge capacity of ZVO@CeO2-3 is 789 mAh g-1 for 100 cycles,and the capacity retention rate is 87.8%,while that of the pure phase is only 65.3%.