Gas-induced bulging in pouch-cell batteries: a mechanical model

TL;DR

This paper develops a homogenised mechanical model to predict gas-induced bulging and internal pressure in Lithium-ion pouch cells, aiding in non-destructive health monitoring and understanding mechanical failure mechanisms.

Contribution

It introduces a new analytical model based on experimental data to predict deformation, stress, and internal gas pressure in pouch-cell batteries.

Findings

Model accurately predicts bulging shape and stress distribution.

Enables estimation of internal gas pressure and SOH without cell disassembly.

Integrates with battery simulations to assess mechanical degradation.

Abstract

Over the long timescale of many charge/discharge cycles, gas formation can result in large bulging deformations of a Lithium-ion pouch cell, which is a key failure mechanism in batteries. Guided by recent experimental X-ray tomography data of a bulging cell, we propose a homogenised mechanical model to predict the shape of the deformation and the stress distribution analytically. Our model can be included in battery simulation models to capture the effects of mechanical degradation. Furthermore, with knowledge of the bending stiffness of the cathode electrodes and current collectors, and by fitting our model to experimental data, we can predict the internal pressure and the amount of gas in the battery, thus assisting in monitoring the state of health (SOH) of the cell without breaking the sealed case.