Unraveling the effects of inter-site Hubbard interactions in spinel Li-ion cathode materials

TL;DR

This study employs advanced density-functional theory with extended Hubbard functionals to accurately predict properties of spinel Li-ion cathodes, highlighting the importance of inter-site interactions for reliable modeling.

Contribution

The paper introduces the use of first-principles computed inter-site Hubbard interactions in DFT+$U$+$V$ to improve modeling of spinel cathode materials.

Findings

V is essential for accurate structural and electronic property predictions.

U captures general property trends but V refines quantitative accuracy.

Method enables first-principles predictions without empirical fitting.

Abstract

Accurate first-principles predictions of the structural, electronic, magnetic, and electrochemical properties of cathode materials can be key in the design of novel efficient Li-ion batteries. Spinel-type cathode materials Li$_x$Mn$_2$O$_4$ and Li$_x$Mn$_{1.5}$Ni$_{0.5}$O$_4$ are promising candidates for Li-ion battery technologies, but they present serious challenges when it comes to their first-principles modeling. Here, we use density-functional theory with extended Hubbard functionals - DFT+$U$+$V$ with on-site $U$ and inter-site $V$ Hubbard interactions - to study the properties of these transition-metal oxides. The Hubbard parameters are computed from first-principles using density-functional perturbation theory. We show that while $U$ is crucial to obtain the right trends in properties of these materials, $V$ is essential for a quantitative description of the structural and electronic properties, as well as the Li-intercalation voltages. This work paves the way for reliable first-principles studies of other families of cathode materials without relying on empirical fitting or calibration procedures.