Mg2+掺杂对正极材料LiFePO4/C结构和电化学性能的影响

摘要

Mg2+ doped LiFePO4/C cathode material was synthesized from LiOH·H2O,Fe(NO3)3·9H2O, and NH4H2PO4 by an aqueous solution method with magnesium acetate as magnesium source. Influence of Mg2+2 doping on the structure, morphology and electrochemical properties of LiFePO4/C cathode material were tested by X-ray diffraction (XRD) , scanning electronmicroscopy (SEM) , Cyclic voltammetry (CV),EIS and galvanostatic charge-discharge test. The results showed Mg2* doping didn' t change olivine structure of IiFePO4. At 0.1 C (1 C = 170 mAh/g) rate, a initial discharge capacity of Mg2+ doped material is 159 mAh/g, but that of undoped material is 153 mAh/g. After 20 cycles, the capacity of Mg2+ doped material is almost no fading. Impedance Rct of the Mg2+ doped material is 322. 8 ft. While that of the undoped material is 463.1 Ω.%以乙酸镁为镁源,用LiOH·H2O、Fe(NO3)3·9H2O、NH4H2PO4为原料通过水溶液法制备了掺杂(Mg2+)的LiFePO4/C正极材料.用XRD、SEM、恒流充放电测试、循环伏安(CV)和交流阻抗谱(EIS)方法,研究了(Mg2+)掺杂对LiFePO4/C的结构、形貌及电化学性能的影响.研究结果表明,(Mg2+)掺杂没有改变LiFePO4橄榄石型的结构；在0.1 C(1C=170 mAh·g-1)的充放电倍率下,Mg2+掺杂使正极材料首次放电比容量从153 mAh·g-1提高到159 mAh·g-1,经20循环次后,容量无损失；电化学交流阻抗显示,掺杂后材料阻抗(Ret)从463.1 Ω减小到322.8 Ω.