Issue 24, 2023

Anion-polarisation-directed short-range-order in antiperovskite Li2FeSO

Abstract

Short-range ordering in cation-disordered cathodes can have a significant effect on their electrochemical properties. Here, we characterise the cation short-range order in the antiperovskite cathode material Li2FeSO, using density functional theory, Monte Carlo simulations, and synchrotron X-ray pair-distribution-function data. We predict partial short-range cation-ordering, characterised by favourable OLi4Fe2 oxygen coordination with a preference for polar cis-OLi4Fe2 over non-polar trans-OLi4Fe2 configurations. This preference for polar cation configurations produces long-range disorder, in agreement with experimental data. The predicted short-range-order preference contrasts with that for a simple point-charge model, which instead predicts preferential trans-OLi4Fe2 oxygen coordination and corresponding long-range crystallographic order. The absence of long-range order in Li2FeSO can therefore be attributed to the relative stability of cis-OLi4Fe2 and other non-OLi4Fe2 oxygen-coordination motifs. We show that this effect is associated with the polarisation of oxide and sulfide anions in polar coordination environments, which stabilises these polar short-range cation orderings. We propose that similar anion-polarisation-directed short-range-ordering may be present in other heterocationic materials that contain cations with different formal charges. Our analysis illustrates the limitations of using simple point-charge models to predict the structure of cation-disordered materials, where other factors, such as anion polarisation, may play a critical role in directing both short- and long-range structural correlations.

Graphical abstract: Anion-polarisation-directed short-range-order in antiperovskite Li2FeSO

Supplementary files

Article information

Article type
Paper
Submitted
28 dec 2022
Accepted
11 apr 2023
First published
12 apr 2023
This article is Open Access
Creative Commons BY license

J. Mater. Chem. A, 2023,11, 13016-13026

Anion-polarisation-directed short-range-order in antiperovskite Li2FeSO

S. W. Coles, V. Falkowski, H. S. Geddes, G. E. Pérez, S. G. Booth, A. G. Squires, C. O'Rourke, K. McColl, A. L. Goodwin, S. A. Cussen, S. J. Clarke, M. S. Islam and B. J. Morgan, J. Mater. Chem. A, 2023, 11, 13016 DOI: 10.1039/D2TA10037A

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