A mathematical model for cyclic aging of spinel LiMn₂O₄/graphite lithium-ion cells

A mathematical model is developed for the cyclic aging of a spinel LiMn₂O₄/graphite lithium-ion cell in this study. The proposed model assumes the formation and dissolution of the solid electrolyte interphase (SEI) in the anode, Mn(II) dissolution of the LiMn₂O₄ cathode active material due to the Mn(III) disproportionation reaction, the effect of deposition of the reduced Mn on the SEI at the anode, and the formation of a cathode-electrolyte interphase (CEI) layer on the cathode. The decrease of the Li-ion diffusion coefficient in the cathode due to the formation of a passive film and the dissolution of the active material are introduced as factors that lead to capacity fading. Temperature effects on the capacity fade parameters and chemical reactions are integrated into this model. The developed model is incorporated into the Newman's Porous Composite Electrode (PCE) framework and implemented in the battery module of COMSOL Multiphysics. The proposed model is used to investigate the effect of variations in the ambient temperature, and of the voltage range of cycling on the capacity fade. In addition, the effect of changes in the volume fraction of cathode active material, the resistance in the cell, and the state of charge of the anode are also studied.