A Finite Strain Model of Stress, Diffusion, Plastic Flow and Electrochemical Reactions in a Lithium-ion Half-cell

TL;DR

This paper develops a comprehensive finite strain model for lithium-ion half-cells, incorporating stress, diffusion, plastic flow, and electrochemical reactions, and demonstrates its ability to predict stress and potential variations consistent with experiments.

Contribution

It introduces a novel continuum model that accounts for finite strains, plastic flow, and stress effects on electrochemical reactions in lithium-ion batteries.

Findings

Stress influences the rest potential via a modified Nernst equation.

Model predictions align well with experimental stress and potential cycles.

The model captures the coupled effects of deformation, diffusion, and electrochemical reactions.

Abstract

We formulate the continuum field equations and constitutive equations that govern deformation, stress, and electric current flow in a Li-ion half-cell. The model considers mass transport through the system, deformation and stress in the anode and cathode, electrostatic fields, as well as the electrochemical reactions at the electrode/electrolyte interfaces. It extends existing analyses by accounting for the effects of finite strains and plastic flow in the electrodes, and by exploring in detail the role of stress in the electrochemical reactions at the electrode-electrolyte interfaces. In particular, we find that that stress directly influences the rest potential at the interface, so that a term involving stress must be added to the Nernst equation if the stress in the solid is significant. The model is used to predict the variation of stress and electric potential in a model 1-D half-cell, consisting of a thin film of Si on a rigid substrate, a fluid electrolyte layer, and a solid Li cathode. The predicted cycles of stress and potential are shown to be in good agreement with experimental observations.