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

Area of Science:

• Materials Science
• Electrochemistry
• Computational Materials Science

Background:

• Cation short-range ordering significantly impacts the electrochemical performance of disordered cathode materials.
• Understanding cation ordering is crucial for designing advanced battery materials.

Purpose of the Study:

• To characterize cation short-range order in the antiperovskite cathode material Li2FeSO.
• To investigate the underlying mechanisms driving short-range ordering and its effect on long-range structure.

Main Methods:

• Density functional theory (DFT) calculations.
• Monte Carlo (MC) simulations.
• Synchrotron X-ray pair-distribution-function (PDF) analysis.

Main Results:

• Predicted partial short-range cation ordering in Li2FeSO, favoring polar cis-OLi4Fe2 configurations.
• Observed preference for polar configurations leads to long-range disorder, consistent with experimental data.
• Anion polarization in polar coordination environments stabilizes these short-range orderings.

Conclusions:

• The absence of long-range order in Li2FeSO is attributed to the stability of polar cis-OLi4Fe2 and other non-OLi4Fe2 motifs.
• Anion polarization is identified as a key factor in directing short-range cation ordering in heterocationic materials.
• Simple point-charge models are insufficient for predicting structures of cation-disordered materials; anion polarization must be considered.