Breathing of a Silicon-Based Anode: Mechanical Discrete Approach Using DEM

Abstract

Silicon is one of the most considered solutions to improve lithium-ion battery technology. Nevertheless, silicon shows a huge expansion, leading to a significant “breathing” of electrodes during cycling, i.e. a succession of swelling and shrinking. Irreversible volume changes are observed and conjectured to be related to microstructure changes. However, current publications addressing the modelling aspects mainly use analytical or continuous models. Thus, this study aims to apply discrete element method (DEM), a granular dynamics numerical tool, on a silicon-based anode in order to consider the complex internal microstructure and the associated micro-mechanics. In particular, a sample of anode was created using the DEM software LIGGGHTS and simplified linear breathing laws of particles were implemented. The global approach follows successive sensitivity analysis of granular/contact parameters to evaluate individually their capacity to reproduce more finely the observed breathing behaviour. So far, it is found that the breathing amplitude is mostly influenced by the silicon fraction and the breathing irreversibility by particles stickiness. The rigidity of particles also had a decreasing influence on swelling amplitude, but only for low values, far from practical ones, and the silicon content within the anode presented a linear influence on the swelling amplitude.