Strain engineering of ion migration in LiCoO2

TL;DR

This study systematically investigates how lattice strain affects Li-ion migration in LiCoO2, revealing strain conditions that can enhance ionic diffusivity and improve battery performance.

Contribution

It provides a comprehensive strain-map for Li-ion diffusion in LiCoO2, demonstrating how tensile and compressive strains influence migration energy barriers.

Findings

Li-ion migration barriers increase with pressure.

Tensile uniaxial c-axis strain reduces migration barriers.

In-plane compressive strain also decreases barriers.

Abstract

Strain engineering is a powerful approach for tuning various properties of functional materials. The influences of lattice strain on the Li-ion migration energy barrier of lithium-ions in layered LiCoO2 have been systemically studied using lattice dynamics simulations, analytical function and neural network method. We have identified two Li-ion migration paths, oxygen dumbbell hop (ODH), and tetrahedral site hop (TSH) with different concentrations of local defects. We found that Li-ion migration energy barriers increased with the increase of pressure for both ODH and TSH cases, while decreased significantly with applied tensile uniaxial c-axis strain for ODH and TSH cases or compressive in-plane strain for TSH case. Our work provides the complete strain-map for enhancing the diffusivity of Li-ion in LiCoO2, and therefore, indicates a new way to achieve better rate performance through strain engineering.