Modeling ionic transport and disorder in crystalline electrodes using percolation theory

TL;DR

This paper reviews how percolation theory models ionic transport in crystalline electrodes, linking microscopic diffusion pathways to macroscopic battery performance, with applications to lithium-ion cathodes and open-source simulation tools.

Contribution

It introduces a lattice percolation framework for modeling ionic conduction in disordered crystalline electrodes, highlighting the impact of disorder and composition on diffusion pathways.

Findings

Diffusion pathways and tortuosity vary with Li content and short-range order.

Percolation thresholds determine ionic conduction efficiency.

Open-source Dribble software facilitates simulations.

Abstract

Solid ionic conductors are essential components of batteries and fuel cells. In many cases, ionic conduction through crystalline materials with substitutional disorder can be modeled with atomic-scale lattice model percolation simulations. The ionic percolation theory reviewed in this chapter describes the percolation behavior of diffusion pathways, identifies the fraction of lattice sites that contributes to ionic conduction, and quantifies the tortuosity of diffusion networks. These quantities can be related to the bulk diffusivity and capacity of intercalation battery electrodes. We discuss applications to lithium-ion battery cathodes in the disordered rocksalt and related crystal structures, showing how the diffusion pathways and their tortuosity vary with the Li content short-range order. All examples are based on the free and open-source Dribble simulation software.