Preliminary Study on the Influence of Internal Temperature Gradient on EIS Measurement and Characterization for Li-Ion Batteries

Battery characteristics in the conditions with/without internal temperature gradient are believed to be different, which imposes difficulty in characterization and modeling of the performance of battery cells, and relatively few studies have conducted the investigation of the effects of thermal gradients on battery characteristics. This paper makes a preliminary study on the influence of internal temperature gradient on EIS (electrochemical impedance spectroscopy) measurement and characterization. Several experiments are designed and implemented to facilitate the investigation. Experimental results and analysis show that the dependence of cell impedance on temperature can be fitted with the Arrhneius law, and the effect of SOC on the impedance is not as much as that of temperature. Moreover, the presence of the temperature gradients decreases the cell impedance when compared to the conditions without temperature gradients, and the higher the gradient, the smaller the amplitude of the measured impedance. With the equivalent circuit model fitting of the EIS measurements, it is found that the temperature gradient mainly influences Rsei and Rct. Based on analysis, a method to use the identified Rsei and Rct under different temperature gradients to re- construct the possible internal temperature distribution of the battery cell is also proposed.