动力锂离子电池电极结构对其极化特性影响的仿真研究

Simulation research of effect of electrode structure on polarization characteristics of power lithium ion battery

基于COMSOL数值仿真平台构建锂离子动力电池电化学-热耦合模型,深入研究了正极材料厚度,正、负极材料颗粒半径与电池内部极化间的作用规律,并在此基础上,归纳阐明了动力锂离子电池放电电压平台衰退、放电周期骤减与电池内部极化间的内在关联。结果表明:正、负极活化极化随正极厚度的增加变化差异较大,正极活化极化在18~31 m V之间波动,而负极可达到260 m V;放电末期负极固相浓差极化急剧增加,最大值达到425 mV。正极颗粒半径对极化的影响较小;负极颗粒半径减小为原来的一半,即0.5Rn时放电中期的负极活化过电势约为55 mV,较1Rn降低45%左右。负极活化极化的增加将导致电池放电电压平台下降,负极活化极化和固相浓差极化在放电末期急剧增加,是电压提前达到放电截止电压的最主要原因。

An electrochemical-thermal model was developed by COMSOL MULTIPHYSICS to analysis the interaction between the thickness of positive,the particle radius of positive and negative electrodes and the polarization.On this basis,the internal relations between the decline of discharge voltage platform,the sharp decrease of discharge cycle and the polarization inside the battery were summarized and illustrated.The results show that the activation polarization of the positive and negative electrodes varies significantly with the increase of the thickness of the positive electrode.The polarization of the positive electrode fluctuates between 18 m V and 31 m V,while the polarization of the negative electrode reaches 260 m V.The concentration polarization of the negative solid phase at the end of discharge increases sharply,and the maximum value reaches 425 mV.While the radius of negative electrode particles is reduced to half of original,which is 0.5R_n,the activation polarization of negative electrode at middle of discharge is about 55 mV,which is about 45%lower than 1R_n.The effect of reducing radius of positive active material particles is not obvious.The increase of activation polarization of negative is the main reason for the decline of the battery discharge voltage platform.The aggravation of activation polarization and concentration polarization of negative solid phase are the main cause of battery voltage reaching the discharge cut-off voltage in advance.