Variation of electrochemical capacitor performance with room temperature ionic liquid electrolyte viscosity and ion size

Fiona B. Sillars, S. Isobel Fletcher, Mojtaba Mirzaeian, Peter J. Hall

Research output: Contribution to journalArticle

Abstract

The use of Room Temperature Ionic Liquid (RTIL) electrolytes promises to improve the energy density of Electrochemical Capacitors (ECs) by allowing for operation at higher voltages. RTIL electrolytes 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4), 1-ethyl-3-methylimidazolium dicyanamide (EMImN(CN)2), 1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (DMPImTFSI), and 1-butyl-3-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMPyFAP) were studied. Tetraethylammonium tetrafluoroborate 1 molar solution in anhydrous propylene carbonate (Et4NBF4-PC 1M) was studied for comparison purposes. Carbon was produced from phenolic resin activated in CO2. The porosity of the carbon samples were characterised by N2 adsorption-desorption at 77 K and the relevant electrochemical behaviour was characterised by galvanostatic charge-discharge, electrochemical impedance spectroscopy and cyclic voltammetry. The highest operating voltage of 3.5 V was obtained for BMPyFAP, whilst the best capacitive performance was obtained for EMImBF4. The maximum energy density increased to 70 Wh kg-1 (carbon) for RTIL EMImBF4 from 35 Wh kg-1(carbon) for the organic electrolyte Et4NBF4-PC 1M. It was found that the performance of the RTIL electrolytes could be related to the IL viscosity and ion size whilst the electrolyte equivalent series resistances produced a linear relationship with viscosity. It was found that the capacitance performance of the RTIL electrolytes followed the order EMImBF4 > DMPImTFSI > BMPyFAP > EMImN(CN)2. The electrolyte and equivalent series resistance were in the order EMImN(CN)2 <EMImBF4 <DMPImTFSI <BMPyFAP.
Original languageEnglish
Pages (from-to)6094-6100
Number of pages7
JournalPhysical Chemistry Chemical Physics
Volume14
DOIs
Publication statusPublished - 2012
Externally publishedYes

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Ionic Liquids
electrochemical capacitors
Electrolytes
Capacitors
electrolytes
Viscosity
Ions
viscosity
Imides
room temperature
liquids
imides
Carbon
ions
carbon
Temperature
flux density
phenolic resins
Tetraethylammonium
Electric potential

Cite this

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title = "Variation of electrochemical capacitor performance with room temperature ionic liquid electrolyte viscosity and ion size",
abstract = "The use of Room Temperature Ionic Liquid (RTIL) electrolytes promises to improve the energy density of Electrochemical Capacitors (ECs) by allowing for operation at higher voltages. RTIL electrolytes 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4), 1-ethyl-3-methylimidazolium dicyanamide (EMImN(CN)2), 1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (DMPImTFSI), and 1-butyl-3-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMPyFAP) were studied. Tetraethylammonium tetrafluoroborate 1 molar solution in anhydrous propylene carbonate (Et4NBF4-PC 1M) was studied for comparison purposes. Carbon was produced from phenolic resin activated in CO2. The porosity of the carbon samples were characterised by N2 adsorption-desorption at 77 K and the relevant electrochemical behaviour was characterised by galvanostatic charge-discharge, electrochemical impedance spectroscopy and cyclic voltammetry. The highest operating voltage of 3.5 V was obtained for BMPyFAP, whilst the best capacitive performance was obtained for EMImBF4. The maximum energy density increased to 70 Wh kg-1 (carbon) for RTIL EMImBF4 from 35 Wh kg-1(carbon) for the organic electrolyte Et4NBF4-PC 1M. It was found that the performance of the RTIL electrolytes could be related to the IL viscosity and ion size whilst the electrolyte equivalent series resistances produced a linear relationship with viscosity. It was found that the capacitance performance of the RTIL electrolytes followed the order EMImBF4 > DMPImTFSI > BMPyFAP > EMImN(CN)2. The electrolyte and equivalent series resistance were in the order EMImN(CN)2 <EMImBF4 <DMPImTFSI <BMPyFAP.",
author = "Sillars, {Fiona B.} and Fletcher, {S. Isobel} and Mojtaba Mirzaeian and Hall, {Peter J.}",
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Variation of electrochemical capacitor performance with room temperature ionic liquid electrolyte viscosity and ion size. / Sillars, Fiona B.; Fletcher, S. Isobel; Mirzaeian, Mojtaba; Hall, Peter J.

In: Physical Chemistry Chemical Physics, Vol. 14, 2012, p. 6094-6100.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Variation of electrochemical capacitor performance with room temperature ionic liquid electrolyte viscosity and ion size

AU - Sillars, Fiona B.

AU - Fletcher, S. Isobel

AU - Mirzaeian, Mojtaba

AU - Hall, Peter J.

PY - 2012

Y1 - 2012

N2 - The use of Room Temperature Ionic Liquid (RTIL) electrolytes promises to improve the energy density of Electrochemical Capacitors (ECs) by allowing for operation at higher voltages. RTIL electrolytes 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4), 1-ethyl-3-methylimidazolium dicyanamide (EMImN(CN)2), 1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (DMPImTFSI), and 1-butyl-3-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMPyFAP) were studied. Tetraethylammonium tetrafluoroborate 1 molar solution in anhydrous propylene carbonate (Et4NBF4-PC 1M) was studied for comparison purposes. Carbon was produced from phenolic resin activated in CO2. The porosity of the carbon samples were characterised by N2 adsorption-desorption at 77 K and the relevant electrochemical behaviour was characterised by galvanostatic charge-discharge, electrochemical impedance spectroscopy and cyclic voltammetry. The highest operating voltage of 3.5 V was obtained for BMPyFAP, whilst the best capacitive performance was obtained for EMImBF4. The maximum energy density increased to 70 Wh kg-1 (carbon) for RTIL EMImBF4 from 35 Wh kg-1(carbon) for the organic electrolyte Et4NBF4-PC 1M. It was found that the performance of the RTIL electrolytes could be related to the IL viscosity and ion size whilst the electrolyte equivalent series resistances produced a linear relationship with viscosity. It was found that the capacitance performance of the RTIL electrolytes followed the order EMImBF4 > DMPImTFSI > BMPyFAP > EMImN(CN)2. The electrolyte and equivalent series resistance were in the order EMImN(CN)2 <EMImBF4 <DMPImTFSI <BMPyFAP.

AB - The use of Room Temperature Ionic Liquid (RTIL) electrolytes promises to improve the energy density of Electrochemical Capacitors (ECs) by allowing for operation at higher voltages. RTIL electrolytes 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4), 1-ethyl-3-methylimidazolium dicyanamide (EMImN(CN)2), 1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide (DMPImTFSI), and 1-butyl-3-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMPyFAP) were studied. Tetraethylammonium tetrafluoroborate 1 molar solution in anhydrous propylene carbonate (Et4NBF4-PC 1M) was studied for comparison purposes. Carbon was produced from phenolic resin activated in CO2. The porosity of the carbon samples were characterised by N2 adsorption-desorption at 77 K and the relevant electrochemical behaviour was characterised by galvanostatic charge-discharge, electrochemical impedance spectroscopy and cyclic voltammetry. The highest operating voltage of 3.5 V was obtained for BMPyFAP, whilst the best capacitive performance was obtained for EMImBF4. The maximum energy density increased to 70 Wh kg-1 (carbon) for RTIL EMImBF4 from 35 Wh kg-1(carbon) for the organic electrolyte Et4NBF4-PC 1M. It was found that the performance of the RTIL electrolytes could be related to the IL viscosity and ion size whilst the electrolyte equivalent series resistances produced a linear relationship with viscosity. It was found that the capacitance performance of the RTIL electrolytes followed the order EMImBF4 > DMPImTFSI > BMPyFAP > EMImN(CN)2. The electrolyte and equivalent series resistance were in the order EMImN(CN)2 <EMImBF4 <DMPImTFSI <BMPyFAP.

U2 - 10.1039/C2CP40089H

DO - 10.1039/C2CP40089H

M3 - Article

VL - 14

SP - 6094

EP - 6100

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

SN - 1463-9076

ER -