用酚醛树脂作炭源对锂离子电池正极材料LiFePO4进行了改性, 用XRD、恒电流充放电等方法研究了酚醛树脂对LiFePO4纯度和电化学性能的影响. 酚醛树脂在高温炭化过程中产生的H2能够和LiFePO4发生反应, 生成Fe2P等物质, 导致材料中活性物质含量降低; 采用先在650℃处理后再于750℃焙烧的方法, 可以显著减少Fe2P等物质的生成, 提高材料的纯度和比容量, 所制备的LiFePO4在0.2C、1C、2C和5C(1C=150mA/g)倍率时的放电比容量分别达到160、150、135和120mAh/g, 并具有较好的循环性能.
Lithium ion battery cathode material LiFePO4/C was prepared by using resorcinol-formaldehyde resin as carbon source. Effects of resin on purity and electrochemical performance of LiFePO4 were investigated by XRD and galvanostatic charge-discharge test. The results indicate that the hydrogen resulted from pyrolysis of resorcinol-formaldehyde resin can react with LiFePO4, then Fe2P, FeP and Li3PO4 are formed. Such impurities will lead the capacity of the materials decrease. The impurities can be reduced significantly by carbonization at lower temperature before calcination at higher temperature. The capacity and cycle property of LiFePO4 are improved greatly by the addition of resorcinol-formaldehyde resin. The specific discharge capacity of LiFePO4 reaches up to 160, 150, 135 and 120mAh/g at 0.2C,1C,2C and 5C(1C=150mA/g) rates, respectively.
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