Quantification of Coulomb Interactions in layered Lithium and Sodium Battery Cathode Materials

TL;DR

This study uses the cRPA method to self-consistently determine Coulomb interaction parameters for layered lithium and sodium battery cathodes, improving the accuracy of first-principles modeling of their properties.

Contribution

It provides systematically calculated Coulomb U and Hund J parameters for key cathode materials, highlighting the local environment's influence over structural variations.

Findings

Coulomb parameters are similar across Li and Na compounds with different stacking.

Variable Coulomb parameters mainly due to localization and screening effects.

Improved agreement with experimental voltages and lattice parameters.

Abstract

Despite the importance of the electron correlation in the first-principles description of the Li-ion cathode materials, the Coulomb interaction parameter, U is often treated as an ad hoc value. In practice, one usually relies on empirical ways of parametric treatment of U to optimally match the experimentally observed physical properties such as band gap or reaction energy. Here, using constrained random phase approximation (cRPA) method, we self-consistently evaluate the Coulomb U and Hund J values for representative layered cathode materials including not only Li compounds but also Na compounds; LiCoO2, LiNiO2, LiMnO2, NaCoO2, NaNiO2, and NaMnO2. We found that the Coulomb interaction parameters for Li and Na compounds and their polymorphs with different layer stackings do not deviate much, which shows the dominant role of local environment rather than of global structural features. We have analyzed the origin of variable Coulomb parameters, which is mainly due to the competition between the localization and screening. We provided cRPA Coulomb parameters for battery cathode materials and validate the values by observing systematic improvement in describing the experimentally observed average intercalation voltage and lattice parameters. These results can be applied for the first-principles calculations as well as model-based simulations for the theoretical investigation of cathode systems.