Studies of xLiFePO4·yLi3V2(PO4)3/C composite cathode materials with high tap density and high performance prepared by sol spray drying method

摘要

The xLiFePO4·yLi3V2(PO4)3/C cathode materials are synthesized by a sol spray drying method. X-ray diffraction results reveal that the xLiFePO4·yLi3V2(PO4)3/C (x,y ≠ 0) composites are composed of LiFePO4 and Li3V2(PO4)3 phases, and no impurities are detected. The samples show spherical particles with the size of 0.5–5 μm, and the tap densities of all the samples are higher than 1.5 g cm−3. Electrochemical tests show that the xLiFePO4·Li3V2(PO4)3/C (x,y ≠ 0) composites exhibit much better performance than the single LiFePO4/C or Li3V2(PO4)3/C. Among all the samples, 3LiFePO4·Li3V2(PO4)3/C possesses the best comprehensive performance in terms of the discharge capacity, average working voltage, and rate capability. At 1, 5, and 10 C rates, the sample shows first discharge capacities of 152.0, 134.3, and 116.8 mAh g−1 and capacity retentions of 99.2, 98.2, and 97.7 % after 100 cycles, respectively. The excellent electrochemical performance of micron-sized xLiFePO4·Li3V2(PO4)3/C (x,y ≠ 0) powders is owing to the homogeneous mixing of reactants at a molecular level by sol spray drying, the incorporation of fast ion conductor Li3V2(PO4)3, and the mutual doping in LiFePO4 and Li3V2(PO4)3.