锂离子电池正极材料LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)过充行为分析

Analysis of overchargeperformance of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2) cathode material for lithium ion cell

通过扣电形式分析不同充电终止电压(4.3、4.5、4.7、4.9和5.1 V)正极材料LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)的性能,研究过充对其性能的影响。结果表明,材料充电到4.9 V后,放电比容量明显降低。通过容量微分曲线分析了材料在整个充放电过程中的相变,H3相的出现导致材料比容量降低。X射线衍射分析表明,材料过充后整体结构并没有发生变化,但有相变产生。平面和截面的扫描电镜图可以看出,材料过充后颗粒破碎严重,内部出现明显裂纹,而且过充后材料的热稳定性明显降低。

The performances of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2) cathode material at different charging cut-off voltage(4.3,4.5,4.7 V 4.9 and 5.1 V)were analyzed to study the effect of overcharge.The results showed that the discharging specific capacity of the material decreased obviously after charging to 4.9 V.The phase transition during the charging-discharging process was analyzed by dQ/dV.The decrease of discharging specific capacity was due to the emergence of H3 phase.The XRD results showed that the whole structure of the material did not change,but had a phase transition.As can be seen from the plane and cross section SEM photos,the breakage of the material was obvious and cracks generated at inner of the material after overcharge.Moreover,the thermal stability of the material also decreased after overcharge.