A multi-physics battery model with particle scale resolution of porosity evolution driven by intercalation strain and electrolyte flow

Abstract

We present a coupled continuum formulation for the electrostatic, chemical, thermal, mechanical and fluid physics in battery materials. Our treatment is at the particle scale, at which the active particles held together by binders, the porous separator, current collectors and the perfusing electrolyte are explicitly modeled. Starting with the description common to the field, in terms of reaction-transport partial differential equations for ions, variants of the classical Poisson equation for electrostatics, and the heat equation, we introduce solid-fluid interaction to the problem. Our main contribution is to model the electrolyte as an incompressible fluid driven by elastic, thermal and lithium intercalation strains in the active material. Our treatment is in the finite strain setting, and uses the Arbitrary Lagrangian-Eulerian (ALE) framework to account for mechanical coupling of the solid and fluid. We present a detailed computational study of the influence of solid-fluid interaction, intercalation strain magnitude, particle size and initial porosity upon porosity evolution, ion distribution and electrostatic potential fields in the cell. We also present some comparison between the particle scale model and a recent homogenized, electrode-scale model.