单分散花状分级结构LiFePO_4的合成及其电化学性能

Synthesis and electrochemical performance of monodisperse flower-like LiFePO_4 with hierarchical architectures

以乙二醇为溶剂,尿素为添加剂,采用溶剂热法制备锂离子电池正极材料磷酸铁锂(LiFePO4)。采用XRD,BET,SEM和TEM等对产物的结构和形貌进行表征,运用恒流充放电测试对LiFePO4/C复合材料的电化学性能进行研究。研究结果表明:花状分级结构的LiFePO4由单晶纳米片组成,且具有开放多孔的特性,其单分散性良好,粒径约为8μm,振实密度达1.2g/cm3。LiFePO4/C样品的首次放电比容量达152.4mA·h/g;在0.2C,1C和2C倍率下比容量分别为134.3,118.5和103.7mA·h/g;当放电倍率为2C时,经过5个循环后,容量保持在100.1mA·h/g,容量保持率为96.7%。

The Li Fe PO4 for Li-ion battery cathode was prepared via solvothermal method using ethylene glycol（EG） as solvent and urea as additive. The crystalline structure and particle morphology of the cathode materials were characterized by high energy synchrotron X-ray diffraction（XRD）, brunauer-emmett-teller（BET）, scanning electron microscopy（SEM） and transmission electron microscopy（TEM）, respectively, and electrochemical properties of the Li FePO4/C composite were tested by constant current source charging and discharging methods. The results indicate that the monodisperse flower-like Li Fe PO4 with the diameter of 8 μm and the tap density of 1.2 g/cm^3 is composed of single crystal nanoplates, and these nanoplates interweave together forming an open porous structure. The initial discharge capacity is 152.4 mA·h/g, and the Li FePO4/C composite delivers a capacity of 134.3, 118.5 and 103.7 mA·h/g at the rate of 0.2C, 1C and 2C, respectively. The discharge capacity is 100.1 mA·h·g^-1 with the capacity retention ratio of 96.7% after 5 charge-discharge cyclings.