电池正极材料Li3V2(PO4)3/C的水热合成和性能

以LiOH·H2O, NH4VO3, NH4H2PO4 和麦芽糖等为原料, 采用水热法合成了碳包覆的磷酸钒锂化合物, 考察了碳含量对材料电化学性能的影响. 利用XRD, TEM, SEM和恒流充放电测试等手段对产物的结构、 形貌和电化学性能进行表征. 结果表明, 在650℃煅烧的样品为单一纯相的单斜晶体结构. 晶体颗粒分布为100~300 nm, 粒度分散均匀, 分散性良好, 无团聚现象, 且在颗粒表面包覆了一层无定形碳, 这有利于改善材料的导电率. 含碳量为10.23%的样品, 在倍率1.0C的电流密度下, 在3.0~4.3 V电压范围内, 样品的首次放电比容量高达118.8 mA·h/g, 循环15圈后放电比容量为115.1 mA·h/g, 容量保持率为96.88%.

Hydrothermal Synthesis and Electrochemical Characteristics of Cathode Materials Li3V2 (PO4)3/C

A novel hydrothermal method was used to synthesize carbon-coated lithium vanadium phosphate compound. LiOH·H2O, NH4VO3, NH4H2PO4 and maltose without further purification were selected as starting materials to prepare precursor and the Li3V2(PO4)3/C which was obtained by sintering precursor at 650℃ for 2 h in flowing argon, and the effects of carbon content on electrochemical properties were investigated. The structural, morphology and electrochemical properties were investigated via X-ray diffraction(XRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM) and constant current charge-discharge cycling. The compound synthesized at 650℃ took on pure monoclinic crystal structure, the particle size of the samples were ranged from 100 nm to 300 nm and there was a layer of carbon on the surface of Li3V2(PO4)3/C particles, which was available for enhancing the conductivity of Li3V2(PO4)3. Electrochemical properties of Li3V2(PO4)3/C were investigated. The results show that the Li3V2(PO4)3/C synthesized at 650℃ exhibits the highest initial discharge capacity of 118.8 mA·h/g and at the 15th cycle, the sample still keeps 115.1 mA·h/g at 1.0C in the voltage range of 3.0-4.3 V with 10.23% carbon contents. This behavior indicates that the Li3V2(PO4)3/C material obtained by hydrothermal method has excellent capacity retention and rate capability.