Effect of calendering on double-layer capacitor electrodes using the discrete element method

This article reports the in-depth analysis, software simulation, and experimental validation of the negative effects of roller compaction on the electrodes of double-layer capacitors, including particle detachment and current collector elongation. The main component of the coatings of double-layer capacitors is porous-particle-type activated carbon containing agglomerates. This study analyzed the interactions between activated carbon particles and agglomerates and constructed electrode models comprising particles of various shapes based on the results of the aforementioned analyses. A bonded particle model implemented in the discrete element method simulation software was employed to simulate and analyze the vertical pressing and bidirectional movements of the particles. Additionally, the simulation results were validated through roller compaction experiments on the electrodes of double-layer capacitors. The results of the simulations and experiments indicated that the roller compaction of double-layer-capacitor electrodes improved their performance and lifespan but lead to various issues such as particle detachment, current collector elongation, and electrode-thickness rebound. Roller compaction degree, compaction speed, and particle shape were found to be the major factors affecting the outcome of calendering. A greater degree of compaction resulted in greater particle detachment, and increased irregularity of particle shapes had a considerable negative impact on electrodes, which can be alleviated by appropriately increasing the compaction speed.