Mechanical and structural analysis simulation of Lithium-Ion Battery electrodes based on inhomogeneous binder distribution

Abstract

Battery simulation reduces safety issues arising from experiments and also improves development cost and speed. Therefore, its importance has been increasing recently along with the advancement of computing speed. Among battery simulation techniques at various scales, Discrete Element Method(DEM) describes the behavior of particles in a battery electrode at the particle level based on Newton's second law. Especially, DEM has strengths in simulating particle interactions and simulating the structural stability of electrodes due to bond formation and destruction between particles. In the battery electrode process, the electrode slurry is coated on a current collector and then goes through a drying process to remove the solvent from the slurry. Binder migration due to solvent evaporation causes an imbalance in the binder distribution of the electrode, which reduces the structural stability of the electrode. Therefore, to simulate a situation where binder is distributed more abundantly at the top of the electrode and less abundantly at the bottom, the contact radius multiplier value was set differently depending on the location within the electrode. This allowed the adhesive strength of the binder, simulated by bonding between active materials, to be set differently. As a comparison group, an electrode with a uniform binder across the entire area was also configurated. The structural stability of the electrode according to the expansion cycle of the electrode was analyzed and compared by setting the case where the binder is non-uniform and the case where the binder is uniform over the entire area of the electrode. The results confirmed that binder inhomogeneity within the electrode due to binder migration accelerates the separation of the electrode and current collector. Furthermore, the numerical values for the number of bonds, bond force, and coordination number were reduced. This showed that the structural instability of the electrode increased. Additionally, this showed a more significant difference between the two cases when the degree of particle expansion was large. This study demonstrates that DEM-based battery electrode simulation can predict electrode fracture during charge-discharge cycling based on interparticle bonding and simulate the structural stability of the electrode.