Simplified electrochemical lithium-ion battery model with variable solid-phase diffusion and parameter identification over wide temperature range

Abstract

Most electrochemical models fail to capture the variable solid-phase diffusion process and low-temperature characteristics of lithium-ion batteries, thereby limiting the model accuracy and their application in extreme climates. This paper develops a simplified yet high-precision electrochemical model for lithium-ion batteries and identifies its parameters over a wide temperature range. First, the thermal-coupled simplified electrochemical model with lumped parameters is presented, in which the concentration-dependent solid-phase diffusion is particularly considered to reflect the real dynamics within solid particles. Second, all model parameters are categorized and stepwise parameter identification is realized by extracting different dynamics from the measured data of the designed tests. Finally, the model is thoroughly verified under galvanostatic discharge tests over the temperature range of −20°C to 45°C. Results show that the proposed model outperforms the model with constant solid-phase diffusion in both voltage and temperature predictions, especially at subzero temperatures. Moreover, based on the validated model, a health-conscious characteristic map for battery power capability prediction is generated by imposing the solid-phase diffusion constraint.