Investigation On The Preparation And Doping Modification Of Li₃V₂（PO₄）₃/C As Cathode For Lithium-Ion Battery

Currently the commercially available anode materials for lithium ion batteries suffer the safety issue as well as the thermal stability.Li3V2(PO4)3 anode material with olivine structure has attracted increasing attention in research field because it has high output voltage,high theoretical specific capacity,and good safety performance.Thus the research on this material has become hotspot particularly the research for improving its conductivity.In this paper the fabrication of doping Li3V2(PO4)3/C cathode material was studied.By using raw material(NH4)2HPO4,V2O5,Li2CO3 and citric acid,Li3V2(PO4)3/C composite doped with metallic oxides was prepared in a freeze-drying method.The dependence of electrochemical performance of Li3V2(PO4)3/C on the calcination temperatures and doping amount of the metal oxides was investigated by XRD,SEM,charge/discharge cycling at constant current,cycle voltammgrams and AC impedance measurements.All doped Li3V2(PO4)3/C exhibited optimum capacity and excellent cycling performance at calcination temperature of 850℃.At the optimum calcination temperature of 850℃,metal doping has no effect on the crystal structure of Li3V2(PO4)3 but decreased the particle size of Li3V2(PO4)3.The cycling stability and capacity was also improved greatly by the metal doping.Li3V2(PO4)3/C doping with 0.04 Na,0.03 Mn and 0.04 Cr showed the highest capacity and best cycling performance.The electrode electrochemical dynamics was studies by cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS).The study shown that the doping increased the diffusion coefficient of lithium ion in Li3V2(PO4)3/C and electrical conductivity as well as the lithium insertion/de-insertion capability.