Dissolution of Complex Metal Oxides from First-Principles and Thermodynamics: Cation Removal from the (001) Surface of Li(Ni₁/₃Mn₁/₃Co₁/₃)O₂

Abstract

The rapid increase in use of Li-ion batteries in portable electronics has created a pressing need to understand the environmental impact and long-term fate of electonic waste (e-waste) products such as heavy and/or reactive metals. The type of e-waste that we focus on here are the complex metal oxide nanomaterials that compose Li-ion battery cathodes. While in operation the complex metal oxides are in a hermetically sealed container. However, at the end of life, improper disposal can cause structural transformations such as dissolution and metal leaching, resulting in a significant exposure risk to the surrounding environment. The transformations that occur between operational to environmental settings gives rise to a stark knowledge gap between macroscopic design and molecular-level behavior. In this study we use theory and modeling to describe and explain previously published experimental data for cation release from Li(Ni₁/₃Mn₁/₃Co₁/₃)O₂ (NMC) nanoparticles in an aqueous environment (Chem. Mater. 2016 (28) 1092–1100). To better understand the transformations that may occur when this material is exposed to the environment, we compute the free energy of surface dissolution, ΔG, from the complex metal oxide NMC for a range of surface terminations and pH.