Issue 9, 2024

Modelling interfacial ionic transport in Li2VO2F cathodes during battery operation

Abstract

Transition metal oxyflourides have gained considerable interest as potential high-capacity cathode materials for Li-ion batteries. So far, commercialization has been hindered by the poor cyclability and fast degradation of this class of materials. The degradation process is believed to start at the surface and progresses toward the bulk. In this context, a suitable cathode-electrolyte interphase (CEI) appears to be a crucial factor where the formation of LiF has been identified as a key component promoting interfacial stability. In the current work, we make use of a combined density functional theory (DFT) and kinetic Monte Carlo (kMC) approach. Using DFT, we determine relevant interfaces between Li2VO2F and LiF. Rejection-free kMC simulations with parameters based on DFT are then used to probe the kinetics in the charging and discharging process of the Li2VO2F phase. We find that the interface formed by joining Li2VO2F and LiF via their most stable surface terminations has a modest but positive effect on the charging rate, where the LiF phase acts as a funnel that facilitates the Li extraction from the bulk of the Li2VO2F phase. However, the same interface has a severe impeding effect on the discharging of partially delithiated structures, which is orders of magnitudes slower than in the charging process. We find that the key property controlling the kinetics in the discharging process is the difference in stability of Li vacancies in the Li2VO2F and LiF phases.

Graphical abstract: Modelling interfacial ionic transport in Li2VO2F cathodes during battery operation

Supplementary files

Article information

Article type
Paper
Submitted
08 3月 2024
Accepted
16 7月 2024
First published
30 7月 2024
This article is Open Access
Creative Commons BY license

Energy Adv., 2024,3, 2271-2279

Modelling interfacial ionic transport in Li2VO2F cathodes during battery operation

J. Kullgren, J. H. Chang, S. Loftager, S. Dhillon, T. Vegge and D. Brandell, Energy Adv., 2024, 3, 2271 DOI: 10.1039/D4YA00163J

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