Ionic transport properties of lithium polysulfides within poly(ethylene-oxide) homopolymer electrolytes

• Published in: Electrochimica acta Vol. 488; p. 144202
• Main Authors: Ahiavi, Ernest, Soudant, Priscillia, Devaux, Didier, Bouchet, Renaud
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-06-2024; Elsevier
• Subjects: Chemical Sciences; Diffusion coefficient; Lithium polysulfides; Material chemistry; Other; Solid polymer electrolyte; Thermodynamical properties; Transference number; Lithium polysulfides; Diffusion coefficient; Solid polymer electrolyte; Thermodynamical properties; Transference number; lithium polysulfides; thermodynamical properties; transference number; diffusion coefficient
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2024.144202

•PEO homopolymer laden with lithium polysulfide is reported.•Ionic conductivity, transference number and diffusion coefficient are reported.•Li2S8 is shown to be more soluble in PEO than Li2S4.•Diffusion of Li2S8 in PEO is slower compared to Li2S4.•Diffusion of anion polysulfides in PEO is strongly hindered compared to TFSI anion.
Lithium-sulfur (Li-S) batteries are attractive due to their high theoretical specific energy density, nonetheless, their upscaling and widespread adaptation have been hampered by issues such as the dissolution and shuttling of lithium polysulfides species (Li2Sx, 2 ≤ x ≤ 8) from the positive electrode through the electrolyte to the negative electrode. The electrolyte medium is thus a decisive factor in tackling the lithium polysulfide shuttle mechanism. In this study, the thermodynamical, structural, and ionic transport properties of Li2Sx within poly(ethylene-oxide), PEO, a solid-polymer electrolyte that can potentially be used in all-solid-state Li-S batteries have been investigated. Results from thermodynamical, infrared spectroscopy and XRD characterizations show that Li2S8 solubilizes better in PEO homopolymer compared to Li2S4 salt. In terms of ionic transport properties, the diffusion measurements via electrochemical methodologies also demonstrate that PEO can slow down the shuttling speed of S82− and S42− by almost two orders of magnitude compared to a conventional liquid electrolyte such as DOL/DME. Long-chain polysulfides in PEO homopolymer show more pronounced shuttling than the short-chain polysulfide. These findings may guide the design of adapted solid polymer electrolytes that can be used as binders or electrolyte separators for all-solid-state Li-S batteries.