Numerical Investigation of Conductivity Additive Dispersion in High-Power and High-Energy NMC-Based Lithium-Ion Battery Cathodes: Application-Based Guidelines

Abstract

Herein, guidelines are provided for the dispersion of conductivity additive in nickel-manganese-cobalt-oxide-based lithium-ion battery (LIB) cathodes with respect to its influence on electrochemical performance. The contrasting design strategies and operating conditions applicable to high-power and high-energy cathodes lead to significant differences in performance limiting factors for the respective microstructures. Hence, a generalization of the optimum dispersion of the conductivity additive that enhances cell performance in all cases is not possible. In this work, four distinct distributions of conductivity additive agglomerate/aggregate sizes resulting from varying mixing conditions are investigated with respect to their compatibility with cathode microstructures intended for different LIB applications with the help of spatially resolved electrochemical simulations. It is found that in the case of high-power cathodes, wherein ionic transport is the dominant performance limiting factor, a more significant proportion of agglomerates that are bigger in size leads to improved diffusion and intercalation conditions. Conversely, in the case of high-energy electrodes wherein the conductivity additive content is minimized, a larger fraction of smaller aggregates, produced by the fragmentation of the agglomerates during the mixing process are essential to ensure sufficient electrical conductivity.