A Simplified Electrochemical and Thermal Aging Model of LiFePO₄-Graphite Li-ion Batteries: Power and Capacity Fade Simulations

Abstract

International audienceIn this paper, an isothermal physics-based agingmodel from the literature is modified and extended to simulate both capacity and power fade of a commercial LiFePO4-graphite Li-ion battery. Compared to the isothermal reference, themechanism of porosity modification due to the Solid Electrolyte Interphase (SEI) film growth at the negative electrode is integrated in the present electrochemical and thermalmodel to establish theoretical correlations between capacity and power fade of the system. The agingmodel includes different contributions of the cell impedance increase such as the SEI film resistance and the electrolyte mass transport resistance due to the mitigation of the negative electrode porosity. Experimental databases from literature and specific experiments coupling endurance tests and Electrochemical Impedance Spectroscopy results, are used to calibrate and validate the correlated power and capacity loss simulations for both calendar and classic galvanostatic cycling operating conditions. The analysis of the experimental data points out that an additional possible aging mechanism such as cracking and fracture of the SEI layer could play an important role for cycling operating conditions and accelerate the electrochemical mechanisms. The impact of physical and design parameters on the power and capacity theoretical correlations are discussed. The limits of applicability of the present model are also discussed in this paper

Statistical Physics-Based Model of Solid Electrolyte Interphase Growth in Lithium Ion Batteries

“…The list of parameters used in the simulations is presented in Table I. Parameters are based on the experimental work of Wang et al 44 and they were extracted by Prada et al 48 …”

A physically meaningful equivalent circuit network model of a lithium-ion battery accounting for local electrochemical and thermal behaviour, variable double layer capacitance and degradation

“…Prada et al's approach is adopted in describing the effects of this layer [24]. The passivation layer overpotential is the voltage drop across the layer:…”

Parameter sensitivity analysis of a simplified electrochemical and thermal model for Li-ion batteries aging

“…[9,10]. The main hypotheses of the model are (1) the expression of current densities now depends on solid and liquid concentrations, (2) a constant electronic conductivity in solid phase is now considered and a mean overpotential in the solid is calculated, (3) migration in the solid phases is not taken into account and (4) electric resistance of connectors is neglected.…”

“…An in-house simplified and computationally efficient electrochemical and thermal model has been developed based on the P2D model [9,10]. Although it was already calibrated for the LiFePO 4 -graphite Li-ion chemistry and shows good results compared to experimental data, the parameter identification process is still a challenging step because of the interdependence of the parameters during the calibration.…”