钼掺杂磷酸钒锂正极材料的制备及其电化学性能研究

以Li2CO3，NH4H2PO4，V2O5和MoO3为原料，柠檬酸为络合剂和碳源，采用溶胶凝胶法制备了锂离子正极材料Li3MoxV2-x(PO4)3/C (x = 0.01, 0.02和0.03). X射线衍射（XRD）表明，合成的材料具有单一的单斜晶系结构，空间群为P21/n. 扫描电镜（SEM）显示Li3Mo0.02V1.98(PO4)3/C具有均一的表面形貌。恒流充放电测试表明，当x = 0.02时，掺杂后的Li3Mo0.02V1.98(PO4)3具有最佳的电化学性能. 在1C倍率下，3.0 ~ 4.3 V电位区间，Li3Mo0.02V1.98(PO4)3/C的首次放电比容量达到122.3 mAh?g-1，循环50周之后，容量没有衰减的迹象；而当x = 0, 0.01和0.03时，首次放电比容量仅分别为117.1 mAh?g-1，115.1 mAh?g-1和116.0 mAh?g-1. 在3C和5C倍率下，样品Li3Mo0.02V1.98 (PO4)3/C仍能保持优异的循环稳定性.

Preparation and Electrochemical Performance of Mo-doped Li3V2(PO4)3/C Cathode Materials

The molybdenum-doped Li3V2-xMox(PO4)3/C (x = 0.01, 0.02 and 0.03) cathode materials were prepared with a sol-gel method by using Li2CO3, NH4H2PO4, V2O5 and MoO3 as raw materials, and citric acid as both chelating reagent and carbon source. The X-ray diffraction (XRD) analyses showed that the crystal structure of as-prepared samples is monoclinic with space group P21/n. Scanning electron microscopy (SEM) observations indicated the uniform morphology for Li3Mo0.02V1.98(PO4)3/C sample. Galvanostatic charge/discharge tests revealed that the optimal Mo-doping proportion is x = 0.02, and the best initial discharge capacity of Li3Mo0.02V1.98(PO4)3/C reaches 122.3 mAh?g-1 in the voltage range of 3.0 ～ 4.3 V at 1C rate with almost no capacity loss after 50 cycles. However, at x = 0, 0.01 and 0.03, the initial discharge capacities are 117.1 mAh?g-1，115.1 mAh?g-1 and 116.0 mAh?g-1, respectively. Even at 3C and 5C rates, the Li3Mo0.02V1.98(PO4)3/C sample also exhibits excellent electrochemical performance.