Impedance Modeling and Aging Mechanisms of the Lithium-ion Batteries using the EIS Technique 2019-01-0596
Along with the rapid progress of electric vehicles (EVs), the battery’s producing and managing technologies attach increasingly general attention. Among them, the methods of estimating the state of health (SoH) and predicting remaining useful life become the focus, which are essential to ensure their reliability and optimum performance over time. This paper mainly focuses on impedance modeling and aging studies (aging diagnosis and life prediction) of lithium-ion batteries. Electrochemical impedance spectroscopy (EIS) technique is used to obtain impedance characteristic of batteries. On the one hand, equivalent circuit modeling can be motivated by EIS, with the goal to fit measured impedance data using circuit elements. On the other hand, the aging research of batteries can be analyzed using the resistance information provided by EIS due to the correlation between battery resistance and lifetime. This paper provides the possible causes of battery aging based on changes in the impedance spectrum, which are obtained under different life conditions through an accelerated life test. According to the result and the corresponding electrode process, an improved Randels model is then established. Combining with the aging mechanism, this paper illustrates the approach of analyzing possible aging causes via the parameter variation, such as the ohmic resistance. Furthermore, a method to predict the battery life based on EIS is proposed. We select the impedance amplitude of a certain frequency as the estimation parameter. The first-order polynomial is finally chosen as the fitting function comparing with the fitting results of various functions. This work gives a deeper understanding of aging mechanisms. The method and advantages of using EIS to estimate the battery life are presented.
Qian GAO, Haifeng Dai, Xuezhe Wei, Bo Jiang