Imidazolium Triflate Ionic Liquids’ Capacitance–Potential Relationships and Transport Properties Affected by Cation Chain Lengths
journal contributionposted on 2021-10-15, 11:28 authored by Niroodha R. Pitawela, Scott K. Shaw
In this paper we report the effects of five imidazolium cations with varying alkyl chain lengths to study the effects of cation size on capacitance versus voltage behavior. The cations include ethyl-, butyl-, hexyl-, octyl-, and decyl-3-methylimidazolium, all paired with a triflate anion. We analyze the capacitance with respect to the cation alkyl chain length qualitatively and quantitatively by analyzing changes in the capacitance–potential curvature shape and magnitude across several standard scanning protocols and electrochemical techniques. Further, three transport properties (viscosity, diffusion coefficient, and electrical conductivity) are experimentally determined and integrated into the outcomes. Ultimately, we find higher viscosities, lower diffusion coefficients, and lower electrical conductivities when the alkyl chain length is increased. Also, capacitance values increase with cation size, except 1-octyl-3-methylimidazolium, which does not follow an otherwise linear trend. This capacitive increase is most pronounced when sweeping the potential in the cathodic direction. These findings challenge the conventional hypothesis that increasing the length of the alkyl chain of imidazolium cations diminishes the capacitance and ionic liquid performance in charge storage.
transport properties affectedthree transport propertiesotherwise linear trendionic liquid performanceimidazolium cations diminishesfive imidazolium cationsfind higher viscositieslower electrical conductivitieslower diffusion coefficientscation chain lengthscapacitance values increasealkyl chain lengthalkyl chainelectrical conductivitydiffusion coefficientcation sizecapacitive increasetriflate anionfindings challengeexperimentally determinedexcept 1electrochemical techniquesconventional hypothesischarge storagecathodic directionanalyzing changes