First-principles study of the impact of grain boundary formation in the cathode material LiFePO4

TL;DR

This study uses first-principles calculations to analyze grain boundary structures in LiFePO4 cathode material, revealing their properties and implications for lithium-ion diffusion in batteries.

Contribution

It provides detailed atomic-level insights into grain boundary structures and energies in LiFePO4 and FePO4, highlighting their roles in lithium migration.

Findings

Grain boundary in LiFePO4 has favorable structural characteristics.

Boundary in FePO4 requires optimization for better Li diffusion.

Interface energies and properties influence lithium mobility.

Abstract

Motivated by the need to understand the role of internal interfaces in Li migration occurring in Li-ion batteries, a first principles study of a coincident site lattice grain boundary in LiFePO4 cathode material and in its delithiated counterpart FPO4 is performed. The structure of the investigated grain boundary is obtained and the corresponding interface energy is calculated. Other properties, such as ionic charges and magnetic moments, excess free volume and the lifetime of positrons trapped at the interfaces, are determined and discussed. The results show that while the grain boundary in LiFePO4 has desired structural and bonding characteristics, the analogous boundary in FePO4 needs to be yet optimized to allow for an efficient Li diffusion study.