Reaction-rate distribution at large currents in porous electrodes

Reaction-rate distribution inside porous electrodes influences the overall performance of Li-ion batteries. The design parameters greatly determine the reaction-rate distribution. Therefore, investigating the relationship between the design parameters and the reaction-rate distribution is vital for improving battery performance. In the present paper, the reaction-rate and current-density distributions are analytically derived across porous electrodes at a short time scale with a Tafel approximation of the Butler-Volmer equation. Three sets of solutions are obtained based on applied currents and design parameters of porous electrodes. In all three sets of solutions, the effective ionic and electronic conductivities are found to shift the reaction from the current-collector to the separator interface. The applied current also influences the reaction-rate and current-density distribution. High C-rates increase the nonuniformity of reaction-rate distribution and the non-linearity of the current distribution. In contrast, low C-rates benefit the uniformity of reaction and linearity of current density.