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

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. • Gas formation during cycling causes the build-up of pressure in a pouch-cell. • Pressure leads to a bulging deformation of the battery. • By modelling the mechanical deformation, we can infer the internal pressure. • We propose a model of the pouch-cell mechanics with limited number of parameters. • We apply our model to estimate the pressure in a real battery from X-ray data.