Combining mechanical and chemical effects in the deformation and failure of a cylindrical electrode particle in a Li-ion battery

TL;DR

This paper develops a comprehensive framework to analyze the coupled mechanical and chemical effects in cylindrical silicon anode particles during lithiation in Li-ion batteries, highlighting buckling risks and stress evolution.

Contribution

It introduces a novel coupled model accounting for plastic deformation and external constraints in cylindrical particles, extending understanding beyond spherical models.

Findings

Plastic deformation occurs throughout the cylinder, not just near the surface.

Stress evolution depends on lithiation rate and external constraints.

Buckling can occur due to axial stress, with a new criterion for swelling-induced buckling.

Abstract

A general framework to study the mechanical behaviour of a cylindrical silicon anode particle in a lithium ion battery as it undergoes lithiation is presented. The two-way coupling between stress and concentration of lithium in silicon, including the possibility of plastic deformation, is taken into account and two particular cases are considered. First, the cylindrical particle is assumed to be free of surface traction and second, the axial deformation of the cylinder is prevented. In both cases plastic stretches develop through the entire cylinder and not just near the surface as is commonly found in spherical anode particles. It is shown that the stress evolution depends both on the lithiation rate and the external constraints. Furthermore, as the cylinder expands during lithiation it can develop a compressive axial stress large enough to induce buckling, which in turn may lead to mechanical failure. An explicit criterion for swelling-induced buckling obtained as a modification of the classical Euler buckling criterion shows the competition between the stabilising effect of radius increase and the destabilising effect of axial stress.