Pore-scale modeling of capillary-driven binder migration during battery electrode drying
This work addresses the need for accurate predictions of binder migration in sodium-ion battery manufacturing to optimize electrode drying processes, though it is incremental as it extends existing spatially resolved models.
The study tackled the problem of binder migration during battery electrode drying by developing a pore-scale continuum model that explicitly describes capillary-driven binder transport, revealing that smaller particle sizes lead to more homogeneous binder distribution while higher evaporation rates and increased surface tension promote stronger gradients.
Sodium-ion batteries employing hard carbon electrodes are considered a drop-in technology for lithium-ion batteries. Electrode drying is a critical manufacturing step, as binder migration during pore emptying impacts the mechanical integrity and electrical performance of the electrode. Existing modeling approaches predominantly rely on the film shrinkage phase in a one dimensional way or neglect the capillary transport, resulting in a lack of physically consistent microstructure resolved predictions of binder migration. In this work, a spatially resolved pore scale continuum model is extended to explicitly describe capillary driven binder transport during pore emptying. The model is applied to hard carbon microstructures with varying mean particle diameters. The simulations reveal that smaller particle sizes lead to a more homogeneous binder distribution, whereas higher evaporation rates and increased surface tension promote stronger binder gradients. Variations in solvent viscosity show only a minor influence on binder migration, as long as no hydrophilic or hydrophobic behavior is present. Finally, the simulations demonstrate that an explicit description of capillary transport and microstructural effects is essential for accurately predicting binder migration and provides a basis for the targeted optimization of electrode drying processes.