A simplified electrochemical modeling method for sodium-ion batteries

Sodium-ion batteries are increasingly becoming important energy storage devices due to their abundant reserves, low cost, and excellent low-temperature performance. As a fundamental part of battery management system, battery modeling plays an essential role in ensuring the efficient and safe operation of sodium-ion batteries. Therefore, this paper proposes a simplified electrochemical model for sodium-ion batteries. Based on the assumptions of single particle model, the solid- and liquid-phase diffusion process, the activation polarization process and the ohmic polarization process are described by discrete algebraic equations. Meanwhile, the parameter identification condition that covers different C-rates is designed, and excitation-response analysis, combined with nonlinear least squares algorithm, is used to identify the model parameters. 1500mAh 18650 NaNi0.5Fe0.5MnO4 batteries are selected to validate the reliability of simulation model. The results turn out that under each working condition, the mean absolute error is less than 50 mV, and the mean relative error is within 2 %, which verifies the accuracy and the applicability under different C-rates of the established model.