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

DOI: 10.1039/D2TA10037A DOI Help

Authors: Samuel W. Coles (University of Bath; The Faraday Institution) , Viktoria Falkowski (University of Oxford; The Faraday Institution) , Harry S. Geddes (University of Oxford; The Faraday Institution) , Gabriel E. Pérez (ISIS Neutron and Muon Source; The Faraday Institution) , Samuel G. Booth (University of Sheffield; The Faraday Institution) , Alexander G. Squires (University of Bath; University College London; The Faraday Institution) , Conn O'Rourke (University of Bath; The Faraday Institution) , Kit Mccoll (University of Bath; The Faraday Institution) , Andrew L. Goodwin (University of Oxford; University of Bath; The Faraday Institution) , Serena A. Cussen (University of Sheffield; The Faraday Institution) , Simon J. Clarke (University of Oxford; University of Bath; The Faraday Institution) , Saiful Islam (University of Bath; University of Oxford; The Faraday Institution) , Benjamin J. Morgan (University of Bath; The Faraday Institution)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Materials Chemistry A

State: Published (Approved)
Published: April 2023
Diamond Proposal Number(s): 27702

Open Access Open Access

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 similar anion-polarisation–directed short-range-ordering may be present in other heterocationic materials that contain cations with different formal charges. Our analysis also 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.

Subject Areas: Materials, Chemistry

Instruments: I15-1-X-ray Pair Distribution Function (XPDF)

Added On: 19/04/2023 11:26


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Physical Chemistry Energy Materials Chemistry Materials Science

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Scattering Total Scattering