(Invited) Solid/Electrolyte Interface Under Confinement in Divalent Water-in-Salt Electrolytes

• DOI: 10.1149/ma2024-01472611mtgabs
• Publication Date: 2024-08-19T15:46:38Z
• Authors: Sarah A. Berlinger; Verena Kuepers; Peter J Dudenas; Devin Schinski; Lucas Q Flagg; Zachary Lamberty; Bryan D. McCloskey; Martin Winter; Joelle Frechette
• Keywords: Interface (matter); Divalent; Fast ion conductor; Salt solution

Concentrated aqueous electrolytes (water-in-salt electrolytes, WiSEs) have gained increasing attention in the last few years because they display much wider electrochemical stability windows (upwards of 3V) than thermodynamic limit water (1.23V), making them exciting candidates for a variety systems including batteries. Importantly, it is ions directly at electrode/electrolyte interface that are key to explaining this unexpected reactivity. The classically thought as electrical double layer (EDL), or ion arrangement an builds up neutralize surface potential. WiSEs present very different EDL structures do classical dilute electrolytes. However, most work has focused on monovalent WiSEs, primarily motivated by Li-battery applications using lithium bis(trifluoromethylsulphonyl)imide (LiTFSI). In work, we aim understand how divalent within WiSE regime alter both short-range and long-range signatures under confinement. For above applications, reactions occur pore-space porous electrode, which exhibit confined, overlapping EDLs. Therefore, use confinement tool probe layering structure (<10 nm) electrostatic decay length (~10-100 away from charged with Surface Forces Apparatus (SFA) measurements. Using comprising LiTFSI, Zn(TFSI) 2 , mixtures two salts, first establish bulk these Wide Angle X-Ray Scattering Raman Spectroscopy, reveal anion cation closely associated all regardless valency. Additionally, clusters formed however, suppressed fraction. Under confinement, SFA results demonstrate thickness adsorbed solid/electrolyte grows Multiple interfacial layers following adlayer, seem dependent size, rather cation. long lengths insensitive This contributes significant fundamental understanding regarding charge-neutralization mechanism class interface.