Mathematical Model for Li-S Cell with Shuttling-Induced Capacity Loss Approximation

© 2020 The Electrochemical Society (“ECS”). Published on behalf of ECS by IOP Publishing Limited Lithium sulfur (Li-S) batteries have the potential to outperform the current lithium ion batteries and transform the technology of the future. However, dissolution, diffusion, and shuttling of the dissolved polysulfides result in parasitic reactions and substantial capacity loss. To provide a better understanding of the shuttling process, a 1D porous electrode mathematical model has been developed in this paper. An approximation method is used to account for the shuttling-induced capacity loss by adding an extra source/sink term in the material balance equations for the species involved in the parasitic reactions. Shuttling constants used in the source terms can be determined by fitting the model predictions to the experimental measurements. The results showed that by including the approximation method, the model was able to predict the active material loss and the continuous decrease of volume fractions of Li2S on the cathode surface. The model sheds light on the capacity loss mechanism occurring inside the cell as a result of the shuttling of polysulfides.