Modeling Oxygen Loss and Phase Transformation in Ni-Rich Cathode Materials: Impact of Electrode Microstructure

Abstract

Nickel-Manganese-Cobalt (NMC) oxides are widely used as cathode materials in lithium-ion batteries. While increasing the nickel content increases the available capacity in a given voltage window, it also reduces the structural stability of the material when cycled to high cutoff voltages. Oxygen release from the crystal structure as well as a layered-to-rocksalt phase transformation of the layered oxide material cause capacity loss and impedance rise. In this work, we propose a continuum approach to model oxygen release and the associated phase transformation using a 1+1D model informed by atomistic simulations to predict the thickness of reconstructed active material over time. An efficient interface model allows us to combine this approach with 3D microstructure-resolved simulations in order to study the effect of a resistive layer on a real cathode microstructure. This novel workflow enables us to investigate the effect of individual electrode properties on the phase transformation and guide future electrode design.