Multi-scale simulation of the adsorption of lithium ion on graphite surface: from Quantum Monte Carlo to Molecular Density Functional Theory

TL;DR

This study combines Quantum Monte Carlo and Molecular Density Functional Theory to accurately simulate lithium ion adsorption on graphite surfaces, highlighting solvent effects on double-layer properties.

Contribution

It introduces a benchmark of DFT functionals with Quantum Monte Carlo data and develops a new pair potential for improved simulation accuracy.

Findings

Adsorption profiles differ significantly between solution and gas phase.

Solvent presence markedly influences the double-layer structure.

Benchmarking reveals strengths and limitations of DFT functionals.

Abstract

The structure of the double-layer formed at the surface of carbon electrodes is governed by the interactions between the electrode and the electrolyte species. However, carbon is notoriously difficult to simulate accurately, even with well-established methods such as electronic Density Functional Theory and Molecular Dynamics. Here we focus on the important case of a lithium ion in contact with the surface of graphite, and we perform a series of reference Quantum Monte Carlo calculations that allow us to benchmark various electronic Density Functional Theory functionals. We then fit an accurate carbon--lithium pair potential, which is used in molecular Density Functional Theory calculations to determine the free energy of the adsorption of the ion on the surface in the presence of water. The adsorption profile in solution differs markedly from the gas phase results, which emphasize the role of the solvent on the properties of the double-layer.