Laurent Guin (Polytechnique)

In Li-ion batteries, the charge carrier Li+ is periodically inserted into and removed from the electrodes, a phenomenon accompanied by electrode swelling (from 10% in graphite to 300% in silicon) and the occurrence of elastic and possibly inelastic deformations. In this talk, we will focus on silicon as an electrode material: a material that undergoes finite strain plastic deformation upon lithium insertion. We will first present a thermodynamically consistent model of the interplay between species diffusion and finite strain inelastic deformation. Second, we will report experimental results of the effect of stress changes on the battery voltage (experiments aimed at probing the dependence on stress of the chemical potential of lithium diffusing in silicon) and discuss them in light of the chemomechanical model. While the main features of the effect of stress on voltage measurements are well accounted for by existing models, we will see how interesting unexplained observations require further modeling of the chemomechanical coupling in the context of inelastic deformation.