Prediction of Lithium Ion Cell Cycle Life By Coupled Chemical and Mechanical Degradation Modeling

Lithium-ion batteries (LIB), owing to their unique characteristics with high power and energy density, are broadly considered as a leading candidate for vehicle electrification. However, the limited cycle life, particularly during fast charging process, is a pivotal performance drawback of LIB. The irreversible formation of the Solid Electrolyte Inter-phase (SEI) at the anode particles surface is identified as a key aging mechanism for these batteries causing capacity loss and resistance rise [1]. Intercalation and deintercalation of Li ions inside the active particles generate significant amount of stress which leads to fracture. Formation of cracks creates new surface area during cycling. These fresh surfaces act as catalysis for SEI formation. At high charge or discharge rates, the diffusion induced fracture and crack propagation exacerbate that results in a higher side reactions rates [2]. Although the tremendous progress in using mathematical models in predicting the cycle life, limited studies have coupled the chemical and the mechanical aspects in cyclic life predictions. The significance of the coupling is manifested during high charge and discharge rates, that the intense intercalation poses high mechanical stresses to fracture the electrode.

In this study, we are investigating the influence of the coupled chemical and mechanical degradation mechanisms on the cycle life of LIB. The computational method comprises of; a first principle capacity fade model for chemical degradation predictions and a stochastic diffusion induced fracture for mechanical damage predictions incorporated in the single particle model [3, 4]. The coupled model is envisioned to present a fundamental elucidation of the high degradation and poor performance during fast charging and discharging rates.

 

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4. R. Deshpande, M. Verbrugge, Y-T. Cheng, J.  Wang, and P. Liu, J. Electrochem. Soc., 159 (10) A1730-A1738 (2012).

 

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