基于电化学衰退模型研究锂离子电池SEI反应

Study on SEI Reaction of Lithium-Ion Batteries Based on the Electrochemical Degradation Model

摘要: 锂离子电池内部的SEI反应是导致电池衰退的重要因素，而SEI反应与电池反应是同时进行的，因此很难用常规的电化学实验方法研究环境因素对其反应的影响。本文基于SEI副反应建立了锂离子电池电化学衰退模型，研究了环境温度对SEI膜生长的影响，得出了SEI膜厚度增长会随着温度升高而增加，高温在一定程度上增加了SEI反应的速率，但温度的提高对SEI膜厚度增长率的影响是有限的。通过分析不同充电、放电倍率所获得的SEI膜厚度增长曲线，得出了SEI膜生长速度随充电倍率增加而加快的结论，但在高倍率放电情况下倍率大小对SEI膜生长影响不大，在低倍率放电情况下，放电倍率越低，SEI膜厚度越厚。另外，分析了不同电极厚度对SEI膜生长的影响，得出了负极厚度越厚SEI膜厚度增加越小，正极对SEI膜生长无直接影响的结论。

Abstract: The SEI reaction in the lithium-ion battery is the crucial factor that makes the battery degradation. It is hard to study the influence of environmental factors on the characteristic of SEI reaction with the conventional electrochemical experiment since the SEI reaction occurs simultaneously with the battery reactions. In this study, the electrochemical degradation model of Li-ion battery was established based on the SEI reaction. The influence of ambient temperature on the growth of SEI film was studied. It was found that the thickness of SEI membrane increased with the elevated temperature. The high temperature (338.15 K < T > 378.15 K) causes, to some extent the increase of the rate of SEI reaction, but its effect on the speed of the increase of SEI film thickness is limited. The growth rate of SEI film increases with the increase of charging rate. In the case of high rates discharge, the rate has little effect on the growth of SEI film. In the case of low rates discharge, the lower the discharge rate is, the thicker the SEI film thickness is. In addition, the effects of different electrode thicknesses on the growth of SEI films were analyzed. The thicker the negative electrode thickness is, the smaller the SEI film thickness is, while the positive electrode thickness had no direct effect on the SEI film growth.