Dynamics of Li-ion in V2O5 Layers from First-Principles Calculations

TL;DR

This study uses first-principles calculations to explore Li-ion diffusion in V2O5 layers, revealing one-dimensional diffusion pathways linked to unstable phonon modes, which could inform better battery electrode designs.

Contribution

It demonstrates the connection between unstable phonon modes and Li-ion diffusion pathways in V2O5 using ab-initio methods, a novel insight for battery material research.

Findings

Li-ion diffusion is one-dimensional along the b-axis.

Unstable phonon modes correlate with diffusion pathways.

Diffusion observed at high temperature (1200 K) in simulations.

Abstract

The alkali atoms, due to their small sizes and low charge ionic states, are most eligible to intercalate in the structural layers of V2O5. We have applied ab-initio density functional theory to study the dynamics of Li-ion in layers of {\alpha}-V2O5. The calculations are performed for two compositions, namely, Li0.08V2O5 and Li0.16V2O5, and show that there are unstable phonon frequencies. The unstable modes have large amplitude of Li atom along the b-axis of the orthorhombic unit cell indicating that such unstable modes could initiate Li-ion diffusion along b-axis. The ab-initio molecular dynamics simulations are performed up to 25 ps at 1200 K, which reveal one-dimensional diffusion of Li atoms. The diffusion pathways of Li atoms from the simulations seem to follow the eigenvectors of the unstable phonon modes obtained in the intercalated structure.