Quantum-mechanics-based molecular dynamics simulations of the structure and performance of sulfur-enriched Li₃PS₄ cathodes

SI Morozov and BV Merinov and T Das and SV Zybin and MY Yang and WA Goddard, CELL REPORTS PHYSICAL SCIENCE, 4, 101326 (2023).

DOI: 10.1016/j.xcrp.2023.101326

Sulfur-enriched Li3PS4 is a promising cathode for lithium-sulfur batteries, but there is not yet clear structural information about this material. Here, we use quantum-mechanics-based molecular dynamics to predict the structures of the fully charged Li3PS4+5 and various stages of discharge to nearly discharged Li3+9PS4+5 at 298 K. We predict that the fully charged cathode has a distorted orthorhombic structure similar to Li3PS4, but with additional S-4 and S-8 chains each linked to an S atom of a PS4 anion. This leads to a density of 2.19 g/cm(3) for this material. For the nearly discharged cathode, we find that the lithium atoms insert into all S-S bonds, with none of the aforementioned chains remaining, leading to a density of 1.71 g/cm(3). We examined the discharge process as lithium ions from the electrolyte diffuse into the cathode and react with the S-S chains to form Li2S. The predicted discharge curve agrees well with the experiment.

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