液相沉淀-多元醇还原法合成LiFePO_4/C正极材料的电化学性能

Electrochemical performance of LiFePO_4/C cathode materials synthesized by liquid-precipitation and polyol reduction route

以钛白工业副产物七水硫酸亚铁为铁源,用液相沉淀制得无定形FePO4·xH2O前躯体,然后在多元醇中与锂源反应制得LiFePO4材料,过程在常压下进行,无需煅烧与惰性气体保护。用XRD、SEM及电化学分析考察多元醇乙二醇(EG)、二甘醇(DEG)和三甘醇(TEG)对材料物相和形貌的影响。结果表明:三甘醇所得样品的锂离子扩散速率最小;此样品的晶粒尺寸最小,结晶最完整,无明显杂相生成。在室温下放电倍率为0.1C、1C和5C时,该正极材料的首次放电比容量分别达到148.8、129.3和102.8 mA·h/g,其碳包覆样品的首次放电比容量分别达到155.6、139.9和112.2 mA·h/g,且循环性能良好。

Amorphous FePO4-xH20 was prepared by liquid precipitation using FeSO4·7H2O by-product of titanium dioxide industry, and LiFePO4 was synthesized by a polyol route under ordinary pressure without further calcinating or inert gas protection. The effects of different polyols of EG, DEG and TEG on the phase composition and morphology were investigated by X-ray diffraction（XRD）, scanning electron microscope （SEM） and electrochemical analysis. The results demonstrate that LiFePO4 prepared by TEG shows the smallest diffusion rate of lithium ion, the smallest particle size, the best crystalline integrity and the highest phase purity. The LiFePO4 prepared by TEG has the first discharge specific capacities of 148.8, 129.3 and 102.8 mA.h/g at 0.1C, 1C and 5C discharge rate and room temperature, respectively. The improved first discharge specific capacity of its carbon-coating sample reaches 155.6, 139.9 and 112.2 mA-h/g at 0.1C, 1C and 5C, respectively, exhibiting a favorable capacity cycling maintenance.