摘要
研究成膜添加剂对材料结构稳定性及LiFePO4/石墨电池高温循环性能的影响。分别测试添加和未添加碳酸亚乙烯酯(VC)的18650电池的高温循环性能,并通过充放电测试、交流阻抗、扫描电镜、X射线能量色散光谱以及拉曼光谱等方法研究VC对电池正、负材料结构的影响。结果表明:VC添加剂在提高石墨结构稳定性的同时显著抑制LiFePO4材料中的溶铁行为;此外,VC添加剂阻止电解液在负极表面还原分解及负极表面SEI膜的增厚,也阻止电解液在LiFePO4电极表面的分解;含有VC添加剂的电解液可以有效改善LiFePO4/石墨电池在高温下的循环稳定性。
Effects of film-forming additive on stability of electrode and cycling performance of LiFePO4/graphite cell at elevated temperature were studied. Two 18650 cells with and without VC additive were investigated by galvanostatic cycling, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis and Raman spectroscopy. The results show that in the presence of VC additive, dissolution of Fe from LiFePO4 material is greatly depressed and stability of graphite structure is improved; the additive can not only reduce reaction of electrolyte on surface of LiFePO4 electrode but also suppress reduction of solvent and thickening of the solid electrolyte interface （SEI） layer on graphite surface. Electrolyte with VC is considered to be a good candidate for improving cycling performance of the LiFePOa/graphite cell at elevated temperature.
基金
Project(2007BAE12B01)supported by the National Key Technology Research and Development Program of China
Project(20803095)supported by the National Natural Science Foundation of China
