Issue 45, 2023

The decisive role of electrostatic interactions in transport mode and phase segregation of lithium ions in LiFePO4

Abstract

Understanding the mechanism of slow lithium ion (Li+) transport kinetics in LiFePO4 is not only practically important for high power density batteries but also fundamentally significant as a prototypical ion-coupled electron transfer process. Substantial evidence has shown that the slow ion transport kinetics originates from the coupled transfer between electrons and ions and the phase segregation of Li+. Combining a model Hamiltonian analysis and DFT calculations, we reveal that electrostatic interactions play a decisive role in coupled charge transfer and Li+ segregation. The obtained potential energy surfaces prove that ion–electron coupled transfer is the optimal reaction pathway due to electrostatic attractions between Li+ and e (Fe2+), while prohibitively large energy barriers are required for separate electron tunneling or ion hopping to overcome the electrostatic energy between the Li+–e (Fe2+) pair. The model reveals that Li+–Li+ repulsive interaction in the [010] transport channels together with Li+–e (Fe2+)–Li+ attractive interaction along the [100] direction cause the phase segregation of Li+. It explains why the thermodynamically stable phase interface between Li-rich and Li-poor phases in LiFePO4 is perpendicular to [010] channels.

Graphical abstract: The decisive role of electrostatic interactions in transport mode and phase segregation of lithium ions in LiFePO4

Supplementary files

Article information

Article type
Edge Article
Submitted
16 Aug 2023
Accepted
24 Oct 2023
First published
07 Nov 2023
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2023,14, 13042-13049

The decisive role of electrostatic interactions in transport mode and phase segregation of lithium ions in LiFePO4

X. Wang, J. Huang, Y. Liu and S. Chen, Chem. Sci., 2023, 14, 13042 DOI: 10.1039/D3SC04297A

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