阳离子Fe位掺杂对LiFePO_4正极材料电化学性能的影响

The Effect of Different Cations Doped in Fe Site on Electrochemical Performances of LiFePO_4 Cathode Material

以蔗糖为碳源,采用高温固相法制备了Fe位掺杂不同阳离子(Al 3+,Ni 2+和Mn2+)的LiFe0.97M0.03PO4/C(M=Al,Ni,Mn)锂离子电池正极材料.用X-射线衍射(XRD)、扫描电镜(SEM)、恒流充放电测试和电化学阻抗谱(EIS)等研究了不同阳离子Fe位掺杂(Al 3+,Ni 2+和Mn2+)对LiFePO4的结构、形貌和电化学性能的影响.结果表明:阳离子Fe位掺杂没有改变LiFePO4的晶体结构,但是减小了LiFePO4材料的粒径,最终改善了LiFePO4的电化学性能.特别是LiFe0.97Mn0.03PO4/C材料具有更好的电化学性能,在0.1C和1C下放电,LiFe0.97Mn0.03PO4/C材料的首次放电比容量分别为162mAhg-1和140mAhg-1,且1C充放电倍率下循环50次后容量保持率仍然为98%.

LiFe0.97M0.03PO4/C（M=Al,Ni,Mn） cathode materials were synthesized by high temperature solid state reaction with sucrose as carbon source. The effect of the different cations doped in Fe site on the structure, morphology and electrochemical performance of LiFePO4 was studied by X-ray diffraction （XRD）, scanning electron microscope （SEM）, galvanostatic charge/discharge tests and electrochemical impedance spectroscopy （EIS）. The results show that cation doped in Fe site did not alter the crystal structure of LiFePO4, but decreased the particle size of the materials, and finally enhance the electrochemical performance of LiFePO4. Especially, the LiFe0.97 Mn0.03 PO4/C showed the best electrochemical performance. The initial discharge capacities of LiFe0.97 Mn0.03 PO4/C at 0. 1 C and 1 C were 162 mAhg-1 and 140 mAhg-1 , and with a capacity retention up to 98% after 50 cycles at 1 C.