Meaning
Physical mechanism of molecular movement determines the speed at which liquid electrolyte molecules migrate through the separator and the porous electrode structure. Efficient solvent transport kinetics are required to maintain a uniform ion concentration across the cell thickness during high-power operation. This property depends on the viscosity of the solvent and the tortuosity of the porous paths.
Diffusion Rate
Molecular movement occurs in response to concentration gradients that form as lithium ions are consumed at the electrode surface. When solvent transport kinetics are slow, the cell experiences high polarization which limits its ability to deliver current. Improving the wetting characteristics of the separator can enhance this rate by reducing the resistance at the liquid-solid interface and allowing for more uniform electrolyte distribution.
Interface Resistance
Formation of the solid electrolyte interphase creates a thin layer that the solvent molecules must bypass. If this layer becomes too thick or dense, solvent transport kinetics drop, leading to localized dry spots in the electrode. These areas become inactive and contribute to the uneven aging of the battery by concentrating current in the remaining active regions.
Process Velocity
Pumping electrolyte into a dry cell during manufacturing requires careful control of the filling speed.
