Mesoscopic modeling and parameter estimation of a lithium-ion battery based on LiFePO4/graphite

A novel numerical model for simulating the behavior of lithium-ion batteries based on LiFePO4 (LFP)/graphite is presented. The model is based on the modified Single Particle Model (SPM) coupled to a mesoscopic approach for the LFP electrode. It comprises one representative spherical particle as the graphite electrode and N LFP units as the positive electrode. All the SPM equations are retained to model the negative electrode performance. The mesoscopic model emphasizes non-equilibrium thermodynamic conditions and employs a non-monotonic open circuit potential for each unit. A parameter estimation study identifies all necessary parameters, including the solid diffusion coefficient and reaction-rate constant of the negative electrode, porosity of both electrodes, initial State-Of-Charge of the negative electrode, initial partial composition of the LFP units, and resistance values. The results show that the mesoscopic model successfully simulates the electrochemical behavior of lithium-ion batteries at varying charge/discharge rates while describing the lithiation/delithiation of LFP particles adequately, although it is computationally more expensive than macro-based models.