Amide-based deep eutectic solvents containing LiFSI and NaFSI salts as superionic electrolytes for supercapacitor applications

Abstract

This work proposes two deep eutectic solvents (DESs) based on lithium bis(fluorosulfonyl)imide and sodium bis(fluorosulfonyl)imide together with N-methylacetamide and formamide as electrolytes for activated carbon (AC) electrochemical double-layer capacitors (EDLCs) at 25 °C. The formulated DESs exhibit a large electrochemical window (ΔE > 2.5 V), good thermal stability (∼150 °C) and ionic conductivity (3–4 mS cm−1), and moderate viscosity (11.3 mPa s). Through the Vogel–Tamman–Vulcher fitting equation, the evolution of pseudo-energy activation was delineated with respect to the nature of the H-bond donor or alkali salt. These electrolytes present a superionic character gleaned from the Walden classification, and their ionicity exceeds that of standard organic electrolytes based on similar alkali salts. The performance of the AC-based EDLC was assessed by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge, yielding 140 F g−1 with an 8% capacity retention during 200 h of floating. Based on the physicochemical properties and electrochemical performance of these DESs, they represent a promising green-alternative electrolyte for supercapacitor applications.

Reline deep eutectic solvent as a green electrolyte for electrochemical energy storage applications

“…For the IR spectrum of Reline, the dominant regions are the N-H and O-H stretching modes located between 3600 and 3000 cm À1 , and the NH 2 bending and CQO stretching bands detected between 1700 and 1600 cm À1 . Remarkably, the structure of the choline-urea mixture remains the same even after the addition of 5% of water, showing that the added water ChCl:butanediol; 63 ChCl:ethylene glycol (EG); 63 ChCl:glycerine; 63 glutaronitrile (GLN):lithium bis[(trifluoromethyl)sulfonyl]imide (LiTFSI); 64 2-methylglutaronitrile (MGLN):LiTFSI; 64 LiTFSI:N-methylacetamide (NMAc); 65 (lithium nitrate) LiNO 3 :NMAc; 39 lithium bis(fluorosulfonyl)-imide(LiFSI):formamide (FMD); 41 tetraethylammonium chloride (TEAC):EG. 40 The blue line is the ''ideal'' Walden product line fixed with 1 mol L À1 aqueous KCl solution.…”

“…Recently, Amara et al proposed the application of the lithium bis(fluorosulfonyl)imide and N -methylacetamide DES as a superionic electrolyte for activated carbon electrochemical double-layer capacitors. 41 Karade reported the use of a DES as an electrodeposition synthesis bath for hybrid supercapacitor electrodes operating in aqueous electrolytes. 42 It is worth noting that there are only a few detailed reports on the application of DESs in the field of electrochemical capacitors (ECs).…”

“…Fig. 2 (a) The Arrhenius plot concerning the ionic conductivity of the Reline DES electrolyte, (b) Walden plot at ambient temperature for: 1choline chloride (ChCl):2urea (Reline) this work ;ChCl:butanediol;63 ChCl:ethylene glycol (EG);63 ChCl:glycerine; 63 glutaronitrile (GLN):lithium bis[(trifluoromethyl)sulfonyl]imide (LiTFSI);64 2-methylglutaronitrile (MGLN):LiTFSI;64 LiTFSI:N-methylacetamide (NMAc);65 (lithium nitrate) LiNO 3 :NMAc;39 lithium bis(fluorosulfonyl)-imide(LiFSI):formamide (FMD);41 tetraethylammonium chloride (TEAC):EG 40. The blue line is the ''ideal'' Walden product line fixed with 1 mol L À1 aqueous KCl solution.…”

Role of FTFSI Anion Asymmetry on Physical Properties of AFTFSI (A=Li, Na and K) Based Electrolytes and Consequences on Supercapacitor Application

“…[16] Various types of liquid electrolytes have been developed for SCs and can be further grouped into aqueous, [17,18] organic, [19,20] ionic liquids [21,22] or deep eutectic solvents. [23,24] In organic media, the electrolytes are composed of salts dissolved in a pure solvent or a mixture of solvents such as nitriles, [25,26] alkylcarbonates [27,28] or ethers. [29] The desolvation energies of ions at polarized interfaces is indicative of faster partial charge transfer kinetics during adsorption desorption in the microporosity.…”

“…By modeling advanced transport properties, it is possible to address the specific role of the cation‐solvent couple [14,15] and to clarify the importance of the anion in the AC‐based EDLC performances [16] . Various types of liquid electrolytes have been developed for SCs and can be further grouped into aqueous, [17,18] organic, [19,20] ionic liquids [21,22] or deep eutectic solvents [23,24] . In organic media, the electrolytes are composed of salts dissolved in a pure solvent or a mixture of solvents such as nitriles, [25,26] alkylcarbonates [27,28] or ethers [29] .…”