Effect of Nb~(5+) doping on high rate performance of LiFePO_4

LiFePO4/C cathode material was prepared by semi-solid phase-carbon-thermal reduction method,using ferric(Fe2O3) as Fe source,LiFe1-xNbxPO4/C(x=0,0.01,0.03,0.05,0.07) composite cathode materials were obtained with high-priced metal ions(Nb5+) doped in Fe site.X-ray diffraction analysis of the crystalline structure of samples indicates that,doping a certain amount of metal ions does not change the crystalline structure of materials.The charge-discharge cycle performance tests show that,doping high-priced ions can improve the electrochemical properties of materials.The specific discharge capacity of the samples is improved greatly and cycling stability is also improved to some extent.Especially in large current field,the advantages are more obvious compared with no metal ions doped LiPePO4/C.LiFePO4/C sample doped with 3% Nb5+ has the best performance,and the first discharge specific capacity is 160.57 mAh/g at 0.1 C,which is still 136.43 mAh/g at 1 C,while at 10 C,the discharge specific capacity still maintains 95 mAh/g.