Modeling the Impact of Thermal Management on Time and Space-Resolved Battery Degradation Rate

The degradation rate of a Li-ion battery is a complex function of temperature and charge/discharge rates over its lifetime. There is obviously a keen interest in predictive electrochemical ageing models that account for known degradation mechanisms, primarily linked with the Solid Electrolyte Interface (SEI) formation and Li-plating, which are highly dependent on the cell temperature. Typically, such ageing models are formulated and employed at pack or cell level, neglecting intra-cell and cell-to-cell thermal and electrical non-uniformities. On the other hand, thermal management techniques can mitigate ageing by maintaining the battery pack within the desired temperature window either by cooling or heating. Inevitably, the cooling of the battery pack by conventional heat exchangers will introduce temperature non-uniformities that may in turn result in undesired intra-cell and/or cell-to-cell health non-uniformities. In this work, an extended multi-dimensional modeling approach is adopted to address intra-cell and cell-to-cell non-uniformities in terms of localized temperature and current. This extension is a key enabler for the prediction of localized temperature and overpotential that determine the rate of the anode deterioration via the formation of Li-plating and SEI. The electrochemical and ageing model parameters are obtained by a combination of literature data and in-house electro-thermal measurements of a pouch cell and a battery module. The model is developed within a commercial software. The study covers thermal management for both active cooling and active heating during battery fast-charging. The results show that inevitable temperature gradients are likely to result in degradation rates that are strongly non-uniform leading to unexpectedly high-capacity loss and resistance increase. The proposed methodology could eventually support the prediction of the battery lifespan as function of thermal design and control parameters at an early development phase.