磷酸铁锂/石墨动力电池衰退机理分析

磷酸铁锂/石墨动力电池作为电动汽车重要的储能载体,探究其衰退机理具有重要意义。研究了四种不同容量保持率(100%、80%、70%、60%)的磷酸铁锂电池的正负极衰退特性,采用电感耦合等离子体发射光谱仪(ICP-OES)、扫描电镜(SEM)、X射线衍射仪(XRD)以及交流阻抗(EIS)等多种表征技术,分析了正负极的比容量、电极形貌、物相组成以及阻抗特性。结果表明,活性锂离子损失造成的电池容量损失主要发生在容量保持率80%之前,而正负电极动力学性能的衰退是电池容量损失的重要原因。随容量保持率的下降,正负极形貌恶化,欧姆电阻、膜电阻、电荷转移电阻均明显增大,正负极脱锂和嵌锂反应难以进行,造成正负极容量损失。

Analysis of Capacity Fading Mechanisms of LiFePO4/Graphite Power Battery

LiFePO4/graphite power battery is an important energy storage carrier for electric vehicles,and exploring its capacity fading mechanism is of great significance.The capacity fading characteristics of negative and positive electrodes of four kinds of lithium iron phosphate batteries with different capacity retention rate(100%,80%,70%,60%)were studied.The specific capacity,morphology,phase composition and impedance characteristics of positive and negative electrodes were analyzed by ICP-OES,SEM,XRD and EIS.The results show that the loss of battery capacity caused by the loss of active lithium ions occurs mainly before the capacity retention rate of 80%,and the fading of the dynamic performance of positive and negative electrodes is an important reason for the loss of battery capacity.With the decrease of capacity retention rate,the morphology of positive and negative electrodes deteriorates,the ohmic resistance,membrane resistance and charge transfer resistance significantly increase,which is contributed to difficulty of lithium extraction-insertion and capacity loss of the positive and negative electrodes.