Charge density and redox potential of LiNiO2 using ab initio diffusion quantum Monte Carlo

TL;DR

This study uses diffusion quantum Monte Carlo to accurately analyze the electronic structure, charge densities, and lithium diffusion barriers in LiNiO2, resolving controversies and improving upon DFT methods.

Contribution

The paper demonstrates the effectiveness of diffusion quantum Monte Carlo in accurately modeling LiNiO2's electronic properties and lithium intercalation characteristics, surpassing traditional DFT approaches.

Findings

DMC accurately captures charge densities and hybridization.

DMC yields precise lithium intercalation voltages.

DFT functionals show limitations in predicting charge polarization.

Abstract

Electronic structure of layered LiNiO2 has been controversial despite numerous theoretical and experimental reports regarding its nature. We investigate the charge densities, lithium intercalation potentials and Li diffusion barrier energies of LixNiO2 (0.0 < x < 1.0) system using a truly ab-initio method, diffusion quantum Monte Carlo (DMC). We compare the charge densities from DMC and density functional theory (DFT) and show that local and semi-local DFT functionals yield spin polarization densities with incorrect sign on the oxygen atoms. SCAN functional and Hubbard-U correction improves the polarization density around Ni and O atoms, resulting in smaller deviations from the DMC densities. DMC accurately captures the p-d hybridization between the Ni-O atoms, yielding accurate lithium intercalation voltages, polarization densities and reaction barriers.