3D Battery Model incorporating large Particle Expansions determining Electrolyte Movement

Abstract

Silicon is a frequently used active material in the negative electrode of lithium ion batteries as it provides substantial improvements in the energy density. Due to large volume changes during cycling, the Si content in state-of-the-art electrodes is typically rather low. As significantly higher Si contents are desirable the effects of structural changes and electrolyte displacements have to be analysed. Accurate models will enable the study of possible local electrolyte depletions in order to mitigate degradation processes and improve cycle life of the batteries. In our work we aim to extend the mesoscopic transport theory of Li-ion batteries by Latz et al. [1] including single phase flow through the porous electrode media. This Darcy flow is generated by the change in Si volume during battery operation. After eliminating the velocity, a discontinuous Galerkin (piecewise constant) formulation equivalent to the finite volume method with upwind schemes is obtained [2]. First toy problems were implemented in Firedrake and tested for convergence properties. Next step is the realisation of the full cell geometry incorporating electrochemical transport. Future work includes the consideration of a radial pseudo dimension within each electrode discretization voxel to account for the diffusion of Li within individual spherical particles and numerical optimization e.g. through stabilizing terms or adaptive mesh refinements. [1] Arnulf Latz et al 2011, Journal of Power Sources 196 3296-3302 [2] Thomas Roy et al 2019, Journal of Computational Physics 395 636–652