碳包埋固相法制备LiFePO4及其电化学性能研究

用石墨粉包埋取代保护性气氛,一步固相法制备LiFePO4.采用XRD,FTIR,SEM和恒电流充放电等方法对材料结构、形貌和电化学性能进行了表征.利用循环伏安法研究了Li+在LiFePO4中的嵌/脱过程.结果表明,这种改进的固相法可以合成亚微米级纯相橄榄石结构LiFePO4,所得材料具有良好的倍率性能和循环稳定性,在0.1C和1C倍率首次放电比容量分别为148.3和131.9mAh.g-1,1C和5C倍率下循环50次容量保持率分别为96%和90%.由循环伏安法计算得到阳极峰和阴极峰处Li+的表观扩散系数分别为1.64×10-13和1.94×10-13cm2.s-1.

Synthesis of LiFePO4 by Solid-State Method with Raw Materials Embedded in Graphite and Electrochemical Properties

LiFePO4 was successfully synthesized as a product via one-step solid-state reaction during which the raw materials were embedded in graphite powder instead of the protective atmosphere when heated at high-temperature. The structure, morphology and electrochemical properties of the product were investigated by XRD, FTIR, SEM and galvanostatic charge/discharge test. The process of lithiation/delithiation of Li⁺ in LiFePO4 electrode was studied by cyclic voltammetry. The results showed that the pure-phase olivine-type LiFePO4 composed of near spherical particles in sub-micrometered size can be obtained by this improved solid-state method. The LiFePO4 thus prepared has favorable multiplication rate and cycling stability. The initial discharge specific capacity is 148.3 and 131.9mAh·g^-1 if the rate is 0.1 C and 1 C, respectively; and after the charge/discharge action cycles 50 times the capacity holding rate is 96% and 90% if the rate is 1 C and 5 C, respectively. As calculated according to cyclic voltammetry, the apparent Li⁺ diffusion coefficients are 1.64×10^-13 and 1.94×10^-13 cm²·s^-1 at the peaks of corresponding CV curves of anode and cathode, respectively.