Numerical optimization of the spatial conductivity distribution within cathode microstructures of lithium-ion batteries considering the cell performance

Abstract

Summary A numerical approach targeting the optimization of the spatial conductivity distribution within a three-dimensional electrode microstructure of lithium-ion batteries is presented. Its methodology is based on a spatially resolved three-dimensional electrochemical model of a lithium-ion battery half cell on the particle scale. Although being independent of the underlying electrode microstructure, the method is exemplarily applied on a computer-generated periodic electrode structure consisting of smooth spherical particles. In the first step, parameter variations are performed to investigate the influence of the electrical conductivity on the simulated half-cell performance. The simulations show that the performance-limiting effect of low electrical conductivity values can be attributed to a through-plane directed inhomogeneity of the local intercalation flux density. Furthermore, it is shown that if a homogenous surface intercalation flux density is reached, a further increase of the spatially uniform conductivity would not result in better half-cell performance. In the second step, the determined optimum spatially uniform conductivity value is taken as a basis for the spatial optimization approach. The resulting conductive structure within the electrode shows gradient-like behavior directed perpendicular to the electrode surface, while highest conductivity values are to be expected in the region close to the current collector. Therefore, multiple layer coating is suggested as a suitable practical manufacturing approach. Due to the proposed two-stage optimization approach, the resulting conductive structure reveals conductivity saving potential without altering the macroscopic cell performance.