化学杂质对尖晶石LiMn_2O_4 电化学性能的影响

采用去离子水清洗以及添加不同Na_2SO_4杂质含量的方法研究了化学杂质对尖晶石LiMn_2O_4材料电化学性能的影响. 电感耦合等离子体发射光谱(ICP-AES)和离子色谱测试表明, 水洗后材料主要杂质元素Na, S均得到有效去除; 电化学测试表明, 水洗后材料放电比容量得到提高, 与含Na_2SO_4杂质LiMn_2O_4材料相比, 水洗后材料在2C常温循环及倍率性能上都明显优于含杂质LiMn_2O_4材料. 通过扫描电子显微镜(SEM)及能量色散谱(EDS)研究了Na, S化学杂质在电池体系中的存在形式及对材料电化学性能的影响. 结果表明, Na_2SO_4溶解于电解液中以及由Na离子在负极还原所引起的副反应将导致电池倍率及循环性能恶化.

Effect of Chemical Impurities on Electrochemical Performance of Spinel LiMn_2O_4 Cathode

The effect of chemical impurities on the electrochemical performance of spinel LiMn_2O_4 cathode was investigated by washing the cathode in deionized water and adding different amount of Na_2SO_4 impurity. Inductively coupled plasma/atomic emission spectrometer (ICP/AES) and ion chromatography results showed that Na and S was successfully eliminated by washing. Compared with impure LiMn2O4, the discharge capacity, the cycle performance and the rate capability were improved after washing. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies on fresh and cycled cathodes were conducted to understand the existing form of Na, S impurities and their effect on electrochemical performance. It was found that Na_2SO_4 dissolved into the electrolyte and Na+ reduced on anode could deteriorate both the rate capability and cycle performance.