Modeling investigation of gradient electrolyte films deposited via convection–diffusion on porous electrode substrates

A numerical simulation based on 1-D upward deposition model has been carried out to investigate the deposition of electrolyte films with gradient microstructures via convection–diffusion process on porous electrode substrates. The simulation results concerning deposition dynamics and structural profiles of the gradient films are in a good agreement with the experimental data. The influences from the solution properties, substrate porosity and evaporation rate of solvent on the microstructural development of deposit layers have been studied by considering the deposition ability and diffusion coefficient of the solute species in porous substrate and the evaporation rate of solvent. It has been found that the concentration distribution in the porous substrate is mainly characterized by a rapid rise up to >10 times its initial value at the deposit–substrate interface and a decaying profile. The uniform deposit layer on the surface of porous substrate and the gradient layer stretching into the substrate are significantly controlled in growth dynamics by the deposition and diffusion abilities of solute for a given evaporation rate of solvent. Moreover, the solute's deposition ability appears to pose more influence on the thickening of top-deposit layer while the diffusion coefficient of solute is the main factor to control the depth development of the gradient layer inside the substrate.