Smoothed Boundary Method Framework for Electrochemical Simulation of Li-ion Battery Cathode with Complex Microstructure: Model, Formulation and Parameterization

TL;DR

This paper introduces a smoothed-boundary method framework for simulating electrochemical processes in complex Li-ion battery cathode microstructures, enabling detailed analysis of microstructural effects on battery performance.

Contribution

The paper develops a novel SBM-based simulation framework that reformulates electrochemical equations for uniform grid solutions using experimental 3D microstructure data.

Findings

Two lithiation models examined: solid-solution and two-phase.

Two-phase lithiation with Fick's diffusion overestimates performance.

Framework reveals detailed microstructural electrochemical dynamics.

Abstract

Rechargeable battery electrodes have highly complex microstructures, consisting of nonuniform electrode particles, tortuous electrolyte channels, and irregular particle-electrolyte interfaces. Moreover, the electrochemical processes involve several coupled physical mechanisms, including mass transport in the electrode particles and electrolyte, current continuity in the solid and liquid, and electrochemical surface reactions. These geometric and mechanistic complexities create a challenging barrier of electrochemical simulations at the microstructural level using conventional methods. In this paper, we introduce a smoothed-boundary method (SBM) electrochemical simulation framework for modeling the electrochemical dynamics of complex battery electrode microstructures. The conventional governing equations are reformulated into SBM versions, and are solved using uniform Cartesian grids. The simulations utilize an image-based, experimentally reconstructed 3D microstructure as the input geometry, and the physical parameters acquired from experimental measurements. Two models of lithiation mechanisms, solid-solution and two-phase, are examined under potentiostatic discharging of a Li$_x$CoO$_2$ composite cathode. Detailed dynamics of the complex cathode microstructure are revealed through the simulations. The comparison between the two models indicates that modeling two-phase lithiation with Fick's diffusion will overestimate the electrode's performance. The presented simulation framework provides an innovative avenue in exploring the electrochemical dynamics at the microstructural level.