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2024 (English)In: Energy Advances, E-ISSN 2753-1457, Vol. 3, no 3, p. 564-573Article in journal (Refereed) Published
Abstract [en]
The solvation structure, dynamics, and transport properties, as well as thermal and electrochemical stabilities of “solvent-in-salt” (SIS) electrolytes, also known as highly concentrated electrolytes, are far from fully understood. Furthermore, these special types of electrolytes are almost without exception based on fluorinated salts. In contrast, here we report on fluorine-free SIS electrolytes comprising ambient temperature liquid sodium bis(2-(2-ethoxyethoxy)ethyl)phosphate (NaDEEP) salt and tris(2-(2-ethoxyethoxy)ethyl)phosphate (TEOP) solvent, for which the ionic conductivities and ion diffusivities are altered profoundly as the salt concentration is increased. A careful molecular level analysis reveals a microstructure with a “solvent-rich” phase with almost an order of magnitude faster ion diffusion than in a “salt-rich” phase. Aggregated ionic structures in these SIS electrolytes lead to higher ionic conductivities alongside lower glass transition temperatures, <−80 °C, but also agreeable thermal stabilities, up to 270 °C, and improved anodic stabilities, possibly up to 7.8 V vs. Na/Na+ and at least >5 V vs. Na/Na+. Altogether, this provides a foundation for both better understanding and further development of fluorine-free SIS electrolytes for sodium batteries.
Place, publisher, year, edition, pages
Royal Society of Chemistry, 2024
National Category
Materials Chemistry
Research subject
Chemistry of Interfaces
Identifiers
urn:nbn:se:ltu:diva-104259 (URN)10.1039/d4ya00002a (DOI)001166636300001 ()2-s2.0-85186486575 (Scopus ID)
Funder
Swedish Research Council, 2020-00969
Note
Validerad;2024;Nivå 1;2024-04-09 (sofila);
Full text license: CC BY 3.0
2024-02-122024-02-122024-06-17Bibliographically approved