锂离子电池正极材料LiFePO4的结构与电化学性能的研究

利用固相法和球化工艺合成了橄榄石型LiFePO4粉体.该粉体由直径为10-15μm的团簇体组成.以合成材料为正极的锂离子电池的循环伏安特性表明,在循环过程中,锂离子插入和脱出具有单一的可逆机制.在不同温度下,材料的交流复阻抗谱表明,随着温度的升高,电池电化学阻抗明显减小.充放电测试结果表明,在17mA/cm2的电流密度下,材料工作电压平稳,电极极化效应较小,容量接近其理论值.在170mA/cm2的电流密度下,电池容量没有明显的减小趋势,而在170mA/cm2电流密度以上时,电池容量迅速降低,且电极极化效应比较显著.经过较大的电流密度测试后,材料在小电流密度下仍然保持着接近理论容量的循环容量.

Structure and Electrochemical Properties of LiFePO4 as the Cathode of Lithium Ion Battery

Oliver phase LiFePO4 powder was successfully synthesized by solid-state reaction process and spherical processing.SEM observation confirmed that the resulatant product consisted of many spherical aggregates with diameters of 10—15 μm.The cyclic voltammetric profile of battery with cathode of LiFePO4 shows the single and reversible mechanism for lithium ion extraction/insertion in cathode.The a.c.impedance spectra of the battery at different temperatures reveal that the electrochemical impedance of battery decreases with increasing ambient temperature.At the current density of 17 mA/cm2,the batteries show a flat working voltage,little electrode polarity effect and nearly theoretical capacity.Below the current density of 170 mA/cm2,the high capacity is kept.With the current density increasing further above 170 mA/cm2,the capacity decreases fast and the electrode polarity effect is observed obviously.After cycling at a high current density,the batteries still show the high capacity at the low current density.