Modelling the calendering process of lithium-ion battery electrodes using the Discrete Element Method (DEM)

The electrochemical performance of a lithium-ion battery is strongly influenced by the microstructure of its electrode. A dried electrode consists of the active material (AM) particles and carbon-binder domain (CBD) phase. One of the important steps in electrode manufacturing is "calendering", where a dried electrode is compressed between heated rollers to obtain a mechanically stable and uniform structure. The effect of calendering pressure on the porosity, tortuosity, and coordination number of an electrode is studied well using DEM. However, a thorough mathematical understanding of the compaction behavior of Li-ion battery electrodes remains largely unexplored. In the present work, we aim to understand the compression behaviour of an electrode using DEM simulations. The simulation domain consists of spherical particles of varying sizes, representing the AM particles. The initial positions, shapes and sizes of the AM are obtained experimentally via XCT [1]. The domain is periodic in the lateral direction, with a moving top wall and a fixed bottom wall. Particle interactions are modelled using Edinburg elasto-plastic adhesive (EEPA) and bond-model, where the bond model captures the mechanical response of CBD phase. Simulations are performed on Altair EDEM. It is shown that porosity and tortuosity obtained from the simulation data are well within the range of experimental values. The pressure-compression behaviour of the simulated structure closely aligns with the powder compaction behaviour described by the Kawakita equation.