title: An Electrolyte for Reversible Cycling of Sodium Metal and Intercalation Compounds.
abstract: Na battery chemistries show poor passivation behavior of low voltage Na storage compounds and Na metal with organic carbonate-based electrolytes adopted from Li-ion batteries. Therefore, a suitable electrolyte remains a major challenge for establishing Na batteries. Here we report highly concentrated sodium bis(fluorosulfonyl)imide (NaFSI) in dimethoxyethane (DME) electrolytes and investigate them for Na metal and hard carbon anodes and intercalation cathodes. For a DME/NaFSI ratio of 2, a stable passivation of anode materials was found owing to the formation of a stable solid electrolyte interface, which was characterized spectroscopically. This permitted non-dentritic Na metal cycling with approximately 98 % coulombic efficiency as shown for up to 300 cycles. The NaFSI/DME electrolyte may enable Na-metal anodes and allows for more reliable assessment of electrode materials in Na-ion half-cells, as is demonstrated by comparing half-cell cycling of hard carbon anodes and Na3V2(PO4)3cathodes with a widely used carbonate and the NaFSI/DME electrolyte.
authors.affiliation: Institute of Chemistry and Technology of Materials, Graz University of Technology, Graz, Austria.
authors.forename: Lukas
authors.identifier: 0000-0002-4103-1060
authors.initials: L
authors.lastname: Schafzahl
authors.affiliation: Institute of Chemistry and Technology of Materials, Graz University of Technology, Graz, Austria.
authors.forename: Ilie
authors.identifier: 0000-0002-9260-9117
authors.initials: I
authors.lastname: Hanzu
authors.affiliation: Institute of Chemistry and Technology of Materials, Graz University of Technology, Graz, Austria.
authors.forename: Martin
authors.identifier: 0000-0001-9706-4892
authors.initials: M
authors.lastname: Wilkening
authors.affiliation: Institute of Chemistry and Technology of Materials, Graz University of Technology, Graz, Austria.
authors.forename: Stefan A
authors.identifier: 0000-0003-2902-5319
authors.initials: SA
authors.lastname: Freunberger
mesh_terms: D002244:Carbon / Q000737:chemistry; D011211:Electric Power Supplies; D004566:Electrodes; D005019:Ethyl Ethers / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry*; D013449:Sulfonamides / Q000737:chemistry*; D014638:Vanadates / Q000737:chemistry
chemical_list: D005019:Ethyl Ethers; D013449:Sulfonamides; D014638:Vanadates; D002244:Carbon; D012964:Sodium; C024683:1,2-dimethoxyethane
keywords: battery; hard carbon; intercalation compounds; sodium; solid electrolyte interface