A Novel Battery Impedance Model Considering Internal Temperature Gradient

Battery models are often applied to describe the dynamic characteristics of batteries and can be used to predict the state of the battery. Due to the process of charging and discharging, the battery heat generation will cause the inhomogeneity between inner battery temperature and surface temperature. In this paper, a novel battery impedance model, which takes the impact of the battery internal temperature gradient on battery impedance into account, is proposed to improve the battery model performance. Several experiments are designed and conducted for pouch typed battery to investigate the electrochemical impedance spectroscopy (EIS) characteristics with the artificial temperature gradient (using a heating plate). Experimental results indicate that the battery internal temperature gradient will influence battery EIS regularly. Using the experimental result without temperature gradient, and with the parameter identification based on particle swarm optimization (PSO), the relationship between impedance and temperature is founded. To obtain the more accurate parameter of battery impedance model considering the influence temperature gradient, we discretize the battery into several slices, which are connected in parallel. The impedance of the entire battery is deemed as the combination of the impedance of each slice. The proposed model is validated with experiments, and the results show that the calculated EIS from the battery model considering the temperature gradient show good accordance to the experimental values and the maximum absolute error is 0.31mΩ, which indicates that, the proposed battery model is a promising alternative for engineering application use.