Mixed Mode Growth Model for the Solid Electrolyte Interface (SEI)

A mixed mode solid electrolyte interphase (SEI) growth model is presented that includes both the influence of the kinetics of the solvent reduction reaction at the SEI/electrode interface and diffusion of the solvent through the SEI layer. The governing equations are solved numerically to predict the solvent concentration profile, the SEI layer thickness, and the capacity loss. Capacity loss predictions are fitted to two sets of experimental data from the literature. The high quality of the fits demonstrates that the mixed mode model provides a useful description of the capacity loss in the cell due to the growth of the SEI layer on the anode under constant voltage storage condition. Also, analytical expressions are presented for SEI growth for both the combined kinetics/diffusion mode (mixed mode model) and the limit of a fast solvent reduction reaction (diffusion limited mode model) as a function of cell characteristics.