Thermal-Electro-Chemical Modeling of Capacity Degradation in Li-Ion Cell

Abstract

Active material dissolution as well as Solid Electrolyte Interface (SEI) film growth are the major factors contributing towards capacity degradation in Li-ion cell. The effect of these factors on capacity fade is exacerbated at high temperature. We propose a thermal-electro-chemical model for studying the effect of both active material dissolution and SEI film growth in a Spinel LiMn2O4/Graphite Li-ion cells. While Mn disproportion reaction has usually been considered as the mechanism of active material loss for modeling purposes, recent studies suggest that the acid attack on Manganese spinel due to electrolyte decomposition causes the dissolution of Mn into the electrolyte. The exact mechanism of Mn dissolution is, however, unknown. In this study we model both mechanisms separately and compare the modeling results. The model is aimed to investigate capacity degradation at different ambient temperature- 25oC, 45oC and 60oC and at different current densities- 0.1C, 1C and 3C. The thermal model is included to study change in temperature due to reversible, irreversible and ohmic heat generation and its subsequent effect on material properties. The results include discharge profiles, film resistance due to SEI film growth, volume changes in electrode and state-of charge of anode.