Simulation of the calendering process of Li-ion electrodes as cohesive granular material: from grain properties to electrode performances

Li-ion batteries are used in many areas of everyday life.Their performance, such as charging rate and energy storage capacity, is strongly influenced by the microstructure of the electrodes and therefore by their manufacturing process, in particular a compaction step called calendering during which the thickness of the electrode is reduced between two rotating cylinders.However, this compaction step also increases the electrode's tortuosity, reducing the battery's charge/discharge rate; a compromise is therefore sought between energy storage capacity and charging rate.The electrode microstructure is a granular medium composed of active particles and a porous matrix of polymer binder.The aim of this thesis work is to model the electrode and the calendering process using a discrete numerical approach, with the goal of better understanding the influence of inter-particle cohesion, confining pressure and compaction rate on the porosity, microstructure and mechanical properties of the electrodes.By means of a detailed parametric study, a scaling law is established for porosity as a function of a dimensionless number, and the influence of the parameters on microstructure is studied and linked with electrical and ionic conductivities. (author)