First-Principles and Thermodynamics Comparison of Compositionally-Tuned Delafossites: Cation Release from the (001) Surface of Complex Metal Oxides

Abstract

<p> Nanoscale complex metal oxides have transformed how technology is used around the world. A ubiquitous example is the class of electroreactive cathodes used in Li-ion batteries, found in portable electronics and electric cars. Lack of recyling infrasructure and financial drivers contribute to improper disposal, and ultimate introduction of these materials into the environment. Outside of sealed operational conditions, it has been demonstrated that complex metal oxides can transform in the environment, and cause negative biological impact through leaching of cations into aqueous phases. Using a combined DFT + Thermodynamics analysis, insights into the mechanism and driving forces of cation release can be studied at the molecular-level. Here, we describe design principles that can be drawn from previous collaborative research on complex metal oxide dissoltuion of the Li(Ni<sub>y</sub>Mn<sub>z</sub>Co<sub>1−y−z</sub>)O2 family of materials, and go on to posit ternary complex metal oxides in the delafossite structure type with controlled release behavior. Using equistoichiometric formulations, we use DFT + Thermodynamics to model cation release. The trends are discussed in terms of lattice stability, solution chemistry/solubility limits, and electronic/magnetic properties. Inercalation voltages are calculated and discussed as a predictive metric for potential functionality of the model materials.</p>