LiFePO_4/C正极材料的液相合成及电化学性能研究

Synthesis and electrochemical properties of LiFePO_4 prepared by using tri-n-butyl phosphate as a multi-function agent

采用磷酸三丁酯(TBP)为多功能反应物并添加表面活性剂PEG-4000合成了LiFePO4/C正极材料,利用XRD、SEM、XPS和滴定分析对产品进行了结构、表面形貌和化学组成表征。结果表明在650℃烧结15h所得产物结晶良好,为均匀分布在100nm左右的类球形颗粒。循环伏安曲线显示,该样品具有对称且尖锐的氧化还原电位峰,表明材料具有良好的电化学可逆性。在0.1mA/cm2电流密度下,其首次充放电比容量分别为162和158mAh/g,经100次循环后放电容量损失率仅为3.3%,当充放电密度增加到4mA/cm2时,材料的放电比容量仍然接近100mAh/g,倍率性能优良。

LiFePO4 cathode material had been synthesized by using tri-n-butyl phosphate（TBP） as a multi-function agent and polyethylene glycol 4000（PEG-4000） as a surfactant and carbon source.The products were detected by means of X-ray diffraction（XRD）,scanning electron microscope（SEM） and X-ray photoelectron spectroscope（XPS）.The results indicated that the sample prepared at 650℃ for 15h was well crystallized with small and homogeneous global particles.In the voltage range of 2.5-4.3V（vs Li）,cyclic voltammetry tests showed there was a pair of sharp redox peaks with almost equal areas,indicating the material an excellent reversibility.Electrochemical tests exhibited that the first discharge capacity was 158mAh/g at the current density of 0.1mA/cm^2.After 100th cycle,the specific discharge capacity was 153mAh/g with only the loss of 3.3%.Even at the high current density of 4.0mA/cm^2,it still showed the discharge capacity close to 100mAh/g.