Nonaqueous Electrolytes for Electrochemical Capacitors: Imidazolium Cations and Inorganic Fluorides with Organic Carbonates

Abstract

Electrolytes based on 1-ethyl-3-methylimidazolium cation (EMI + ) and either the hexafluorophosphate (EMIPF 6 ) or tetrafluorborate (EMIBF 4 ) anion in organic alkyl carbonate solvents have been evaluated for use in electrochemical capacitors. The conductivity, capacitance, limiting oxidation and reduction potentials, and thermal stability were assessed. High conductivity and capacitance values were found regardless of whether cyclic (high viscosity/high dielectric constant) or acyclic (low viscosity/low dielectric constant) alkyl carbonates were used. The best correlation with conductivity for the EMIPF, salt was found to be the molecular weight (K-1/Mw) and to a lesser degree the viscosity (Kc1/i) of the solvent. The high specific capacitance (130 F/g) and excellent stability (>3.5 V, >130°C) make these electrolytes well suited for use in electrochemical double-layer capacitors.

Carbons, Ionic Liquids, and Quinones for Electrochemical Capacitors

“…At their inception (Wilkes and Zaworotko, 1992), it was suggested that RTILs might be important electrolyte materials for capacitor devices and this view has stood the test of time (Hagiwara and Lee, 2007;Arbizzani et al, 2008;Wolff et al, 2015), with early works involving the aromatic imidazolium and pyridinium cations (McEwen et al, 1997;McEwen et al, 1999;Ue and Takeda, 2003).…”

Wearable electrochemical sensors for monitoring performance athletes

“…They have indeed become "designer solvents" with many ILs now being designed for a specific application, for example as potential electrolytes for various electrochemical devices [15][16][17][18][19][20][21][22][23][24][25][26][27] , including rechargeable lithium cells, [28,29] solar cells, [30][31][32] actuators [33][34][35] and double layer capacitors (DLCs). [36][37][38] Along with electrochemical applications, ILs have gained momentum in bio applications. Recent work in the area include ILs as biocatalytic reactions [27,39] , biosensors [40] , protein stabilization [41] and biopreservation [42] .…”

Application of Ionic Liquids to Double‐Layer Capacitors

“…A moderate capacitance around 25 F g À1 was obtained for 1000 charge-discharge cycles at 2.0 V, but its capacitance faded rapidly at 3.0 V down to 40% after 3500 cycles, as shown in the top panel of Table 17.3. After this study the research group changed to use ionic liquids as the supporting electrolyte salt in the organic solvents, and this was probably due to the bad low temperature characteristics [24,[43][44][45][46][47][48]. EMIAlCl 4 was also tested for double-layer capacitor using carbon black, but the charge-discharge efficiency was very low (52 $ 32%) because the electrolyte decomposed at a high cutoff voltage (3.5 $ 4.0 V) and the capacity was also low, as shown in the lower panel of Table 17.3, due to inappropriate selection of carbon material [49].…”