Physical–Chemical Characterization of Binary Mixtures of 1-Butyl-1-methylpyrrolidinium Bis{(trifluoromethyl)sulfonyl}imide and Aliphatic Nitrile Solvents as Potential Electrolytes for Electrochemical Energy Storage Applications

Abstract

In the scope of improving the energy and power densities of electrochemical double layer capacitors (EDLCs), the development of high performance electrolytes with enhanced operative voltages is imperative. The formulation of mixtures containing ionic liquids with organic molecular solvents is an important strategy in the pursuit of developing highly electrochemically stable and safe materials while retaining fast transport properties for high power applications. In this work, we report on the physical–chemical investigations into binary mixtures containing the ionic liquid 1-butyl-1-methylpyrrolidinium bis­{(trifluoromethyl)­sulfonyl}­imide with one mononitrile solvent, butyronitrile, and two dinitrile solvents, glutaronitrile and adiponitrile, as potential electrolytes for EDLCs. The thermal, volumetric, and transport properties of the binary mixtures are investigated as functions of the electrolyte composition and temperature. Furthermore, the electrolyte composition which exhibits the highest conductivity for each of the binary mixtures was determined, and its electrochemical stability is reported using a glassy carbon macrodisk electrode.

Thermophysical Characterization of TFSI Based Ionic Liquid and Lithium Salt Mixtures

“…As expected, density increases with salt concentration. Density values for pure IL are in very good concordance with the findings of other authors [6,7]. With regards to the speed of sound (Figure 2), similar behaviours were observed, with a decrease in this parameter with the temperature for pure IL and its mixtures.…”

“…Figure 5. Similar values of conductivity of pure [bmpyr] [TFSI] have been found by other authors [6,9]. A clear decrease in electrical conductivity was detected when increasing the salt concentration.…”

In Situ Preparation of Crosslinked Polymer Electrolytes for Lithium Ion Batteries: A Comparison of Monomer Systems

“…Therefore, the development of safer electrolytes has been intensively pursued following different concepts that are summarized in a number of excellent reviews [ 3 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. The concepts included (i) replacement of moisture-sensitive salts with less sensitive conducting salts, e.g., salts with non-coordinating anions with extensive charge delocalization, such as lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) [ 9 , 15 , 16 ]; (ii) substitution of the flammable organic liquids by non-flammable ionic liquids [ 8 , 17 , 18 , 19 , 20 , 21 , 22 ] with negligible vapor pressure [ 23 , 24 ]; (iii) incorporation of conducting salts into a swollen polymer (gel electrolytes) [ 20 , 25 , 26 , 27 ]; (iv) incorporation of conducting salts into dry polymers to yield solid polymer electrolytes, often reported with poly(ethylene oxide) (PEO) as the matrix to yield solid state electrolytes (SSE) [ 28 , 29 ]; (v) substitution of salts with polymers with ionic sites (often polymeric ionic liquids, PIL) [ 7 , 8 , 12 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ]; (vi) complete replacement of organics by Garnet-type ceramics [ 38 , 39 ]; and recently, vii) preparation of organic/inorganic hybrids with inorganic nanoparticles such as TiO 2 to boost ionic conductivity and lithium transference numbers [ 31 , …”

Materials for supercapacitors: When Li-ion battery power is not enough

“…In the last years, several nitrile-based electrolytes such as glutaronitrile (GTN) [49][50][51], adiponitrile (ADN) [51][52][53][54][55][56], butyronitrile (BTN) [54,55], and 2-methylglutaronitrile (2-MGN) [51], have been investigated as replacements of ACN. These solvents have been used in combi nation with Et 4 NBF 4 as well as other conducting salts [49][50][51][52][53][54][55][56][57]. They typically display lower ionic conductivities compared to ACN-based electrolyte.…”