A control oriented reduced order electrochemical model considering variable diffusivity of lithium ions in solid

Abstract

Recently, reduced order electrochemical models (ROMs) have been obtained more attention by industries for real-time applications. Its computational efficiency is maximized by regarding particles in electrodes as an equivalent single particle, named ROM-Single Particle Model (SPM). However, the model has a major drawback in the inaccuracy of the predicted terminal voltage, particularly at high currents. Therefore, an advanced ROM-SPM considering variable diffusivity (VD) of lithium ions in solid is proposed that significantly improves the accuracy of the terminal voltage, named as ROM-SPMVD. The model is firstly developed, and the sensitivity analysis of the parameters is performed, which reveals that the diffusivity of lithium ions in solid of cathode (Ds,p) is strongly sensitive and identifiable. Next, the relationship between the Ds,p and state of charge (SOC) and temperature is determined by a newly developed nondestructive method. Finally, the ROM-SPMVD is validated against experimental data of a pouch type lithium ion energy cell at different current profiles and at different temperatures. Results show that consideration of variable Ds,p leads to a significant improvement in the accuracy of the ROM-SPM at high currents while maintaining the reduced computational time. The voltage error of ROM-SPMVD is reduced up to 79% compared with that of ROM-SPM.