Analyzing and Improving Conductive Networks in Commercial High-Energy Ni-rich Cathodes

Abstract

Nickel-rich stoichiometries such as NMC811 have gained increasing relevance for lithium-ion-batteries in recent years due to their high specific capacity and reduced use of critical resources. However, low intrinsic electronic conductivity of NMC active materials makes the use of carbon-based additives necessary. Volume fraction and distribution of the carbon-binder-domain (CBD) have a significant impact on the electrode performance. This work combines high-resolution tomography and microstructure-resolved simulations to characterize the three-dimensional transport networks of a commercial NMC811 cathode. FIB-SEM tomography reveals that low CBD volume fractions with suboptimal distribution cause a non-percolating conductive network in the microstructure and thus unfavourably low electronic conductivity. Increasing the CBD content through virtual electrode design enables percolation and enhances electronic conductivity fundamentally. Simulations on both the real and virtually designed structures demonstrate how percolating CBD networks lead to a significantly improved energy density.