动力锂电池性能衰减过程内部结构分析研究

Analysis of internal structure of performance deterioration for power lithium-ion battery

以电动汽车退役动力锂离子电池(退役电池)、报废动力锂离子电池(报废电池)为研究对象,利用扫描电镜(SEM)、X射线能谱仪(EDS)、X射线衍射仪(XRD)、电化学充放电仪、内阻测试仪、气相色谱仪等仪器研究电池外特性衰退过程电极表面形貌及活性物质材料的理化特性,研究引起动力锂离子电池性能衰减的原因。研究结果表明:电极活性物质和导电剂的溶解与脱落,电极材料粒径尺寸和形貌变化,以及负极表面SEI膜重复再生是导致动力锂离子电池性能衰减的主要原因。此外,上述情况的发生导致电池内部不断产生气体,电池内阻增大,电极极化加剧。

For the purpose of studying the origination of battery performance deterioration, the physical and chemical properties of active materials for retired and spent power lithium-ion batteries of electric vehicles were investigated by scanning electron microscopy （SEM）, energy dispersive X-ray spectrometry （EDS）, X-ray diffraction （XRD）, charging/discharging test, battery internal resistance tester and gas chromatograph, respectively. The results indicate that the performance deterioration of power batteries is mainly due to the dissolution and loss of active materials and conductive additive, the deterioration of surface morphology and particle size of active materials or the repeated destruction and formation of solid electrolyte interface （SEI） film on anode surface, respectively. Furthermore, the swollen phenomenon, increase of internal resistance and electrode polarization are appeared during the process of battery performance deterioration.