Extensive Sodium Metal Plating and Stripping in a Highly Concentrated Inorganic−Organic Ionic Liquid Electrolyte through Surface Pretreatment. Issue 5 (23rd February 2017)

• Record Type: Journal Article
• Authors: Basile, Andrew; Makhlooghiazad, Faezeh; Yunis, Ruhamah; MacFarlane, Douglas R.; Forsyth, Maria; Howlett, Patrick C.
• Is Part Of: ChemElectroChem. Volume 4:Issue 5(2017)
• Page Start: 986
• Page End: 991
• Publication Date: 2017-02-23
• Subjects: energy storage -- organic ionic plastic crystal -- inorganic−organic ionic liquid -- solid-electrolyte interphase -- sodium metal; Electrochemistry -- Periodicals; 541.37
• DOI: 10.1002/celc.201600784
• Languages: English
• ISSNs: 2196-0216

Abstract

Abstract: In the present work, the stable and extensive cycling of Na plating and stripping is demonstrated within an inorganic−organic ionic liquid electrolyte. The electrolyte is composed of liquid‐state tri(isobutyl)methylphosphonium bis(fluorosulfonyl)imide when employing a high 45 mol % Na concentration in the form of sodium bis(fluorosulfonyl)imide. The liquid‐state electrolyte supports safe Na metal electrochemistry at 50 °C and exhibits a conductivity of 10 −2.5 S cm −1 . Through plating/stripping with 1 h polarization times (12 cycles, J =0.5 mA cm −2 ), a surface is prepared with a smooth surface devoid of dendrites and, importantly, a stable solid‐electrolyte interphase, determined by using scanning electron microscopy and impedance spectroscopy. After this, a greater mass transfer can be undertaken through an increased polarization time of 5 h (Q=2.5 mAh cm −2 ) for a duration of 120 h. Abstract : Aim high : An initial high potential during the primary half cycle is absent upon opposite polarization when using a pre‐cycled Na foil in a Na|Na cell comprising a highly concentrated 45 mol % NaFSI in tri(isobutyl)methylphosphonium bis(fluorosulfonyl)imide electrolyte. Successive cycles at 2.5 mAh cm −2 (5 h half cycle, J =0.5 mA cm −2 ) provide a stable voltage‐time profile, a smooth surface morphology and decreased interfacial resistance.