热解条件对LiFePO_4/C表面自由能的影响

Effect of Pyrolytic Reaction Conditions on Surface Free Energy of LiFePO_4/C Composite

以葡萄糖为碳前驱体对水热合成的磷酸铁锂粉末进行碳包覆.测定磷酸铁锂粉末与三种探测液的接触角,并据此通过Young方程采用Wu方法计算了粉末的表面自由能.研究了表面自由能与电导率、放电比容量的关系及对工业化涂布性能的影响.结果表明,在电导率相同的前提下,粉末表面自由能中色散分量与极性分量的比值(γd/γp)对低倍率放电性能没有影响,但对高倍率放电性能影响较大.提高热解温度和延长热解时间可使γd/γp值增加,这有利于粉体与聚偏氟乙烯(PVdF)的粘合和高倍率放电容量的提高.

Lithium iron phosphate powders were prepared by hydrothermal synthesis, and coated using glucose as carbon precursor. The contact angles for calculating surface free energy of LiFePO4 powders with three probe liquids were measured. The surface free energy and its dispersive part and polar part were calculated, based on Young equation and the method suggested by Wu. The relations of surface free energy to conductivity, coating property and specific capacity were studied. The results indicated that with the same conductivity, the dispersive/polar ratio of surface free energies （SE） of the powders had no effect on low rate discharge capability, whereas had great effect on high rate discharge capability. The higher temperature and longer time of pyrolytic reaction led to an increase of the dispersive/polar ratio, which was beneficial for its adhesion with polyvinylidene fluoride （PVdF） and the enhancement of high rate discharge capability.