Porous Agglomerate Model for Battery Electrodes and Application to the Lithium-Silicon System

A treatment is developed for porous electrodes consisting of porous agglomerates, with the porous agglomerates consisting of solid (primary) particles of active material. With the use of the multi-site, multi-reaction formulation, gradients of the chemical potential of Li are the driving force for solid-state diffusion, and the different Li species and reaction sites are employed in the electrochemical kinetics equations. The method is applied to the Li-Si electrode system, including the impact of protective coatings over the active materials. The numerical analysis treats the full pseudo-three-dimensional problem, and histories and profiles of the potentials and concentrations are elucidated. The overall procedure can facilitate rational battery design and construction, including attendant trade-offs for selection of key physical dimensions and material alternatives that govern the cell performance.