新型正极材料LiFePO_4的电化学性能的改进

Improvement of electrochemical performance of LiFePO_4 as a novel cathode material

为解决锂离子蓄电池新型正极材料LiFePO4的低导电率的问题,采用高温固相法合成出包覆碳并掺杂了少量Mg2+的LiFePO4样品。采用X射线衍射、充放电测试、交流阻抗和循环伏安测试方法,深入研究了包覆碳后Mg2+掺杂对LiFePO4结构和电化学性能的影响。研究结果表明,包覆碳后掺杂少量的Mg2+能进一步提高LiFePO4的导电性,从而提高材料的比容量和循环性能。不同的Mg2+离子掺杂量(x=0.02、0.04、0.06、0.08)里,Li0.94Mg0.06FePO4的电化学性能最佳,以0.1C充放电,首次放电比容量为141.9mAh/g,充放电效率为93.1%;循环50次后,容量几乎没有衰减。

To solve the problem of low conductivity in LiFePO4 as novel cathode material for lithium ion battery, a small quantity of Mg^2＋-doped and carbon-coated LiFePO, samples have been prepared by high temperature solid-state reaction method. The effect on the structure and electrochemical performance of carbon-coated LiFePO4 by Mg^2＋ ion doping was investigated intensively by X-ray diffraction, charge-discharge tests, alternating current impedance and cyclic voltammetry method, The results show that the conductivity of carbon-coated LiFePO, is improved by Mg^2＋ ion doping, so the capacity and cycle performance of the material are increased. In the different amounts of doping Mg^2＋ ion（x=0.02, 0.04, 0.06, 0.08）, the electrochemical performance of Li0.94Mg0.08FePO4 is the best. As Li0.94Mg0.08FePO4 is charged and discharged at 0.1C, its first specific discharge capacity and chargedischarge efficiency are 141.9 mAh/g and 93.1% respectively. After 50 cycles, its capacity has no decay.