Semi-Empirical Modeling of Capacity Fade: A Practical Approach for Battery Pack Manufacturers

The growing demand for lithium ion batteries with long lifetime and warranty presents significant challenges for battery pack manufacturers to sufficiently understand cell ageing while keeping testing and validation costs low. To keep up with the rapid deployment of new cell types, appropriate modeling can be used to extrapolate limited-duration empirical results. We have implemented a semi-empirical modeling approach for predicting capacity fade under various operating conditions, using physics-based degradation mechanisms that provide a good fit to experimental data. Good agreement between the model and empirical results is demonstrated for two state-of-the-art 18650 cell types. The major improvement of this work over other approaches is that it minimizes the testing necessary to validate the unique capacity fade of each new cell type, allowing pack manufacturers to rapidly and accurately down-select the best candidate cells for specific applications.