Surface reconstruction and phase transformations of nickel rich electrodes are major components of degradation in nickel rich oxides. These transformations at the surface modify the structure and propagate into the bulk through cation disorder and oxygen vacancies, affecting the long term capacity of a battery. To gain a physical and electrochemical understanding of degradation at nickel rich cathodes, we propose a general first-principles based theory from electrostatics and statistical mechanics to study the dynamics of cation disorder and phase transformations of nickel rich cathodes. We apply a oxygen vacancy boundary condition and perform cycling simulations using the chemical potential model formulated in a porous electrode model to simulate degradation increase during battery lifetime, where we find good agreement with previous experimental data and atomic level simulations at different voltage cutoffs considered in simulations. This work provides a much needed model for cation degradation at the particle level scale for porous electrode modeling to predict and prevent disorder driven capacity fade in nickel-rich electrodes.

Describing layered oxide cathode degradation through cation disorder defect models

ACS Spring 2022

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