Ionic liquids in supercapacitors

Brandt, Adrian; Pohlmann, Sebastian; Varzi, Alberto; Balducci, Andrea; Passerini, Stefano

doi:10.1557/mrs.2013.151

Cited by 269 publications

(242 citation statements)

References 44 publications

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“…ILs are salts usually 25 consisting of poorly interacting anions and cations; due to these weak interactions they display relatively low melting temperatures (<100ºC). [17][18][19][20][21] In addition, ILs typically possess several other physical properties that are desirable in EDLC electrolytes, such as non-flammability, high thermal and chemical stability, and due to their inherent low volatility can be considered to be less hazardous than organic 30 solvent based electrolytes. 17,22 Physical properties other than the ESW of ILs play a crucial role in their performance as electrolytes and vary considerably with the structure of their constituent ions.…”

Section: Introductionmentioning

confidence: 99%

“…25 The most widely studied cations are pyrrolidinum or imidazolium based 17 . When coupled with the [Tf 2 N] anion, pyrrolidinium based electrolytes are typically stable in the region of 3.5V; however, their relatively high viscosity results in poor 5 performance at high rates.…”

Section: Introductionmentioning

confidence: 99%

“…17,23,[26][27][28] Imidazolium [Tf 2 N] electrolytes, on the other hand, tend to be less viscous at room temperature but are less electrochemically stable and are limited to operating potentials around 3.2V. 17,20,23,29,30 For example, the conductivity of 1-butyl-3-methylpyrrolidinum [Tf 2 N] is in the region of 2.2mScm -1 24 whereas 1-ethyl-3-methylimidazoium [Tf 2 N] is 3.4mScm -1 . 29 There is 10 therefore a compromise between the quantity of energy stored in an IL based EDLC and the rate at which this energy can be delivered.…”

Section: Introductionmentioning

confidence: 99%

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Ionic liquid based EDLCs: influence of carbon porosity on electrochemical performance

2014

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Electrochemical double layer capacitors (EDLCs) are a category of supercapacitors; devices that store charge at the interface between electrodes and an electrolyte. Currently available commercial devices have a limited operating potential that restricts their energy and power densities. Ionic liquids (ILs) are a promising alternative electrolyte as they generally exhibit greater electrochemical stabilities and lower volatility. This work investigates the electrochemical performance of EDLCs using ILs that combine the bis(trifluoromethanesulfonyl)imide anion with sulfonium and ammonium based cations. Different activated carbon materials were employed to also investigate the influence of varying pore size on electrochemical performance. Electrochemical impedance spectroscopy (EIS) and constant current cycling at different rates were used to assess resistance and specific capacitance. In general, greater specific capacitances and lower resistances were found with the sulfonium based ILs studied, and this was attributed to their smaller cation volume. Comparing electrochemical stabilities indicated that significantly higher operating potentials are possible with the ammonium based ILs. The marginally smaller sulfonium cation performed better with the carbon exhibiting the largest pore width, whereas peak performance of the larger sulfonium cation was associated with a narrower pore size. Considerable differences between the performance of the ammonium based ILs were observed and attributed to differences not only in cation size but also due to the inclusion of a methoxyethyl group. The improved performance of the ether bond containing IL was ascribed to electron donation from the oxygen atom influencing the charge density of the cation and facilitating cation–cation interactions.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ionic liquid based EDLCs: influence of carbon porosity on electrochemical performance

2014

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“…Among various ionic liquid electrolytes, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF 4 ) has received considerable attention as a promising electrolyte in EDLC due to its low viscosity and high ionic conductivity [24,25]. However, imidazolium-based ionic liquids typically exhibit poor reductive stability at lower potentials, and thus it is reductively decomposed on the negative electrode during cycling of EDLCs with high operating voltages [26]. Pyrrolidinium (Pyr)-based ionic liquids can be an alternative ionic liquid electrolyte for EDLC applications due to their high electrochemical stability and hydrophobic nature [27,28].…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Characterization of Electric Double Layer Capacitors Assembled with Pyrrolidinium-Based Ionic Liquid Electrolytes

Cho

Shin

Kim

et al. 2016

Journal of Electrochemical Science and Technology

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We present the electrochemical performance of electric double layer capacitors (EDLCs) assembled with pyrrolidinium (Pyr)-based ionic liquid electrolytes at 55 o C. Cations with various alkyl chain lengths were employed in Pyr-based ionic liquids to investigate the effect of cation structure on the cycling stability of EDLCs. The EDLCs exhibited initial specific capacitances ranging from 122.4 to 131.6 F g −1 based on activated carbon material at 55 o C. Cycling data and XPS results demonstrate that Pyr-based ionic liquid with longer alkyl chain is more effective for enhancing the cycling stability of EDLC by suppressing the reductive decomposition of pyrrolidinium cations during cycling at high temperatures.

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“…Room temperature ionic liquids are used in diverse fields ranging from solvents in chemical synthesis [1,2], to electrochemical supercapacitors [3] and lubricants [4]. The non-volatility and wide electrochemical window of stability of ionic liquids render them good candidate electrolytes for electrochemical and energy storage applications, especially in nanodevices where a large voltage is applied over small length-scales (for a recent review of ionic liquids at electrified interfaces, see [5]).…”

Section: Introductionmentioning

confidence: 99%

Unravelling nanoconfined films of ionic liquids

Lee

Vella

Perkin

et al. 2014

The Journal of Chemical Physics

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The confinement of an ionic liquid between charged solid surfaces is treated using an exactly solvable 1D Coulomb gas model. The theory highlights the importance of two dimensionless parameters: the fugacity of the ionic liquid, and the electrostatic interaction energy of ions at closest approach, in determining how the disjoining pressure exerted on the walls depends on the geometrical confinement. Our theory reveals that thermodynamic fluctuations play a vital role in the "squeezing out" of charged layers as the confinement is increased. The model shows good qualitative agreement with previous experimental data, with all parameters independently estimated without fitting.

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Ionic liquids in supercapacitors

Abstract: Abstract

Cited by 269 publications

References 44 publications

Ionic liquid based EDLCs: influence of carbon porosity on electrochemical performance

Ionic liquid based EDLCs: influence of carbon porosity on electrochemical performance

Electrochemical Characterization of Electric Double Layer Capacitors Assembled with Pyrrolidinium-Based Ionic Liquid Electrolytes

Unravelling nanoconfined films of ionic liquids

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