碳含量对磷酸钒锂电化学性能的影响

The Influence of Carbon Content on Electrochemical Properties of Lithium Vanadium Phosphate

以LiOH·H2O、NH4VO3、NH4H2PO4和葡萄糖为原料,采用水热法制备碳包覆的磷酸钒锂化合物,利用XRD、SEM、TEM、恒流充放电测试、交流阻抗测试等手段,对产物的结构、形貌和电化学性能进行表征,研究了碳含量对材料电化学性能的影响。结果表明,在750℃焙烧的样品为单一纯相的单斜晶体结构,颗粒大小约1μm,分散性良好,且在颗粒表面包覆了一层无定形碳。在倍率0.1 C的电流密度下,在3.0~4.8 V电压范围内,碳含量为10.63%的样品首次放电容量达到163.6 m Ah/g;循环50次后,放电容量仍为156.5 m Ah/g,容量保持率为95.7%。

A carbon-coated Li3V2 （PO4 ）3/C was synthesized by a hydrothermal route. In this route, LiOH H20, NH4VO3, NH4H2PQ and glucose were selected as starting materials to prepare sample. The structure and electrochemical properties of the LVP/C were characterized by X-ray diffraction, scanning and transmission electron microscopy, galvanostatic charge-discharge cycling, and electrochemical impedance spectra. The influence of carbon content on electrochemical performance of Li3V2 （PO4 ）3/C was discussed. Experiment results show that, the sample roasted at 750 ℃C is a pure phase with monoclinie crystal structure, the particle size is about lum, and has good dispersibility. Moreover, a layer of amorphous carbon is coated on the surface of the particles. The sample with 10. 63% carbon content exhibits highest initial discharge capacity of 163.6mAh/g at 0. 1 C between 3.0 and 4.8 V. And the sample exhibits discharge capacity of 156.5mAh/g with capacity retention ratio of 95.7% after 50 cycles.