Lattice-Particle Microstructural Model for Ion Diffusion in Graphite Electrode Batteries

Abstract

In this work, we propose a lattice-particle approach to study ionic diffusion across graphite electrodes. In our approach, we generate virtual representative volume elements (RVE) of the electrode material based on its composition, i.e., active particles, carbon additives, and binder. Porosity is also accounted for as an input parameter. To account for the evolution of the ionic concentration, Fickean diffusion is considered. This problem is solved within a network of one-dimensional elements, which is constructed upon the particles of the RVE, yielding a three-dimensional lattice. We use the central- difference time-integration scheme to solve the transient problem within the framework of the finite element method for the spatial discretization. One of the main advantages of our approach is that we are able to reduce the number of degrees of freedom and thus the computational cost in comparison to the conventional continuum-based finite element simulations. For the transport simulations, we consider Li ions, although our approach can be also applied to other type of species, such as PF− 6 anions in the case of DIGB with LiPF6 electrolyte, for instance. Finally, we analyze the effect of microstructural features of graphite electrodes on transport properties such as the effective diffusivity.