不同SOC和温度下锂电池超高频阻抗特性研究

Study of Ultra-high Frequence Impedance Characteristics of Lithium Batteries at Different SOC and Temperature

锂离子电池电化学阻抗谱(EIS)可用于电池荷电状态(SOC)和温度状态监测。然而现有研究主要关注在中低频段(<1 kHz),而对更高频段的EIS特性缺乏研究。对不同SOC和温度下的锂离子电池超高频(UHF)阻抗特性进行研究。首先,通过锂离子电池的UHF模型理论分析了SOC和温度对阻抗实部和虚部的作用规律;然后提出了高频脉宽调制(PWM)开关振荡响应的锂离子电池UHF阻抗在线测量方法;最后,在18650单体和电池模组上进行了实验验证。理论分析和实验结果表明:UHF段的锂离子电池等效阻抗对SOC和温度的敏感性远远高于低频段。在240 kHz下,电池等效阻抗均随着SOC的减小而增大。但是等效电抗几乎不受温度的影响,等效电阻会随着温度的升高而增大。

Electrochemical impedance spectroscopy(EIS)for lithium-ion batteries can be used to monitor battery state of charge(SOC)and temperature conditions.However,existing studies mainly focus on the low and mid-frequency bands(<1 kHz),and there is a lack of research on the EIS characteristics of higher frequency bands.The ultra highfrequence(UHF)impedance characteristics of lithium-ion batteries at different SOC and temperature are studied.Firstly,the effect of SOC and temperature on the real and imaginary parts of the impedance is analyzed by the UHF model theory of lithium-ion batteries.Then,an online measurement method for UHF impedance of lithium-ion batteries with high-frequency pulse width modulation(PWM)switching oscillation response is proposed.Finally,experimental verification is carried out on the 18650 battery and battery module.Theoretical analysis and experimental results show that the equivalent impedance of lithium-ion batteries in the UHF band is much more sensitive to SOC and temperature than that of the low frequency band.At 240 kHz,the equivalent impedance of the cell increases as the SOC decreases.However,the equivalent reactance is almost unaffected by temperature,and the equivalent resistance increases with increasing temperature.