Improved electrochemical properties in the Li_3Fe_2(PO_4)_3 by titanium and vanadium doping  

作　　者：Zhengshen Hua Xin Zhang Xiaojing Feng Xiaoran Wang Jun He Xin Wang Huifen Peng 

机构地区：[1]School of Material Science & Engineering, Hebei University of Technology [2]Research Institute for Energy Equipment Materials, Hebei University of Technology [3]Tianjin Key Laboratory of Laminating Fabrication & Interface Control Technology for Advanced Materials

出　　处：《Chinese Chemical Letters》2019年第3期792-796,共5页中国化学快报（英文版）

基　　金：supported by Natural Science Foundation of Hebei Province (No. E2016202358)

摘　　要：The nominal Li_(3-x)Fe_(2-x)Ti_x(PO_4)_(2.55)(VO_4)_(0.45)(x=0～0.3) compounds were synthesized by a sol-gel process.Different from the single V043 doping, further introduction of Ti^(4+) ion was easy to result in precipitation of a little secondary phases, besides the main NASICON products. The simultaneous substitution of Ti^(4+)and VO_4~3 for Fe^(3+) and PO_4~3,respectively, in the Li_3 Fe_2(PO_4)_3 resulted in a net improvement in the rate capability and cycling performance, as compared with the single Ti^(4+) or VO_4~3-substituted compound.The sample with x=0.2 presented a high initial discharging capacity of 125.4 mAh/g at the rate of 0.5 C,about 25% higher than the Ti^(4+)-substituted Li_(2.8)Fe_(1.8)Ti_(0.2)(PO_4)_3, and 102.6 mAh/g after 60 cycles at 2 C,about 12% higher than the single VO_4~3-substituted one. The high rate performance between 0.5 C to 10 C suggested that this sample had a good stability and reversibility. These results proved that the combination of the Ti^(4+) substitution for Fe^(3+) with the V043 substitution for PO_4~3 was a promising method of improving electrochemical performance of the studied Li_3 Fe_2(PO_4)_3 cathode material.The nominal Li_(3-x)Fe_(2-x)Ti_x(PO_4)_(2.55)(VO_4)_(0.45)(x=0～0.3) compounds were synthesized by a sol-gel process.Different from the single V043 doping, further introduction of Ti^(4+) ion was easy to result in precipitation of a little secondary phases, besides the main NASICON products. The simultaneous substitution of Ti^(4+)and VO_4~3 for Fe^(3+) and PO_4~3,respectively, in the Li_3 Fe_2(PO_4)_3 resulted in a net improvement in the rate capability and cycling performance, as compared with the single Ti^(4+) or VO_4~3-substituted compound.The sample with x=0.2 presented a high initial discharging capacity of 125.4 mAh/g at the rate of 0.5 C,about 25% higher than the Ti^(4+)-substituted Li_(2.8)Fe_(1.8)Ti_(0.2)(PO_4)_3, and 102.6 mAh/g after 60 cycles at 2 C,about 12% higher than the single VO_4~3-substituted one. The high rate performance between 0.5 C to 10 C suggested that this sample had a good stability and reversibility. These results proved that the combination of the Ti^(4+) substitution for Fe^(3+) with the V043 substitution for PO_4~3 was a promising method of improving electrochemical performance of the studied Li_3 Fe_2(PO_4)_3 cathode material.

关 键 词：Li3Fe2(PO4)3 LITHIUM ion battery CATHODE DOPING ELECTROCHEMICAL property 

分 类 号：O6[理学—化学]