Room Temperature Molten Salts Research Articles

Physicochemical Investigation of Adiponitrile-Based Electrolytes for Electrical Double Layer Capacitor

Herein, we present the formulation and the characterization of novel adiponitrile-based electrolytes as a function of the salt structure, concentration, and temperature for supercapacitor applications using activated carbon based electrode material. To drive this study two salts were selected, namely, the tetraethylammonium tetrafluoroborate and the 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide. Prior to determination of their electrochemical performance, formulated electrolytes were first characterized to quantify their thermal, volumetric, and transport properties as a function of temperature and composition. Then, cyclic voltammetry and electrochemical impedance spectroscopy techniques were used to investigate their electrochemical properties as electrolyte for supercapacitor applications in comparison with those reported for the currently used model electrolyte based on the dissolution of 1 mol·dm–3 of tetraethylammonium tetrafluoroborate in acetonitrile. Surprisingly, excellent electrochemical performances were observed by testing adiponitrile-based electrolytes, especially those containing the 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide room-temperature molten salt. Differences observed on electrochemical performances between the selected adiponitrile electrolytes based on high-temperature (tetraethylammonium tetrafluoroborate) and the room-temperature (1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide) molten salts are mainly driven by the salt solubility in adiponitrile, as well as by the charge and the structure of each involved species. Furthermore, in comparison with classical electrolytes, the selected adiponitrile +1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide solution exhibits almost similar specific capacitances and lower equivalent serial resistance. These results demonstrate in fact that the adiponitrile +1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide mixture can be used for the formulation of safer electrolytes presenting a very low vapor pressure even at high temperatures to design acetonitrile-free supercapacitor devices with comparable performances.

Stable Quasi-Solid-State Dye-Sensitized Solar Cells Using Novel Low Molecular Mass Organogelators and Room-Temperature Molten Salts

Stable quasi-solid-state dye-sensitized solar cells (DSCs) were fabricated by using room-temperature molten salts (1-methyl-3-hexyl-imidazolium iodide), and a series of diamine derivatives with different lengths of alkyl chain as low molecular mass organogelators (LMOGs). The number of methylene (-CH2-) units between the two amide carbonyl groups in the gelator molecule has significant influence on the charge transport property of gel electrolyte, and the kinetic processes of the electron transport and recombination. Less compact networks of the ionic liquid gel electrolytes containing odd-numbered -CH2- gelator facilitate the diffusion of I-3(-) and I-. Also, the odd-numbered -CH2- gelators-based DSCs exhibit longer electron recombination lifetime and a higher open circuit potential (V-oc) compared with the DSCs based on even-numbered -CH2- gelators; consequently, the photovoltaic performances of DSCs based on odd-numbered -CH2- gelators are much better than those even-numbered -CH2- gelators. Remarkably, the results of the accelerated aging tests showed that the ionic liquid gel electrolyte-based DSCs could retain 93%-99% of their initial photoelectric conversion efficiencies (eta) under heat at 60 degrees C, and 100% of their initial photoelectric conversion efficiencies under one sun light soaking with UV cutoff filter at 50 degrees C for 1000 h. This excellent long-term stability of quasi-solid-state DSCs is very important for application and commercialization of DSCs.

The Effect of Hydrophilic Ionic Liquids 1-Ethyl-3-Methylimidazolium Lactate and Choline Lactate on Lipid Vesicle Fusion

Ionic liquids (ILs) are room-temperature molten salts that have applications in both physical sciences and more recently in the purification of proteins and lipids, gene transfection and sample preparation for electron microscopy (EM) studies. Transfection of genes into cells requires membrane fusion between the cell membrane and the transfection reagent, thus, ILs may be induce a membrane fusion event. To clarify the behavior of ILs with cell membranes the effect of ILs on model membranes, i.e., liposomes, were investigated. We used two standard ILs, 1-ethyl-3-methylimidazolium lactate ([EMI][Lac]) and choline lactate ([Ch][Lac]), and focused on whether these ILs can induce lipid vesicle fusion. Fluorescence resonance energy transfer and dynamic light scattering were employed to determine whether the ILs induced vesicle fusion. Vesicle solutions at low IL concentrations showed negligible fusion when compared with the controls in the absence of ILs. At concentrations of 30% (v/v), both types of ILs induced vesicle fusion up to 1.3 and 1.6 times the fluorescence intensity of the control in the presence of [Ch][Lac] and [EMI][Lac], respectively. This is the first demonstration that [EMI][Lac] and [Ch][Lac] induce vesicle fusion at high IL concentrations and this observation should have a significant influence on basic biophysical studies. Conversely, the ability to avoid vesicle fusion at low IL concentrations is clearly advantageous for EM studies of lipid samples and cells. This new information describing IL-lipid membrane interactions should impact EM observations examining cell morphology.

Ionic Liquid of a Gold Nanocluster: A Versatile Matrix for Electrochemical Biosensors

Ionic liquids are room-temperature molten salts that are increasingly used in electrochemical devices, such as batteries, fuel cells, and sensors, where their intrinsic ionic conductivity is exploited. Here we demonstrate that combining anionic, redox-active Au25 clusters with imidazolium cations leads to a stable ionic liquid possessing both ionic and electronic conductivity. The Au25 ionic liquid was found to act as a versatile matrix for amperometric enzyme biosensors toward the detection of glucose. Enzyme electrodes prepared by incorporating glucose oxidase in the Au25 ionic liquid show high electrocatalytic activity and substrate affinity. Au25 clusters in the electrode were found to act as effective redox mediators as well as electronic conductors determining the detection sensitivity. With the unique electrochemical properties and almost unlimited structural tunability, the ionic liquids of quantum-sized gold clusters may serve as versatile matrices for a variety of electrochemical biosensors.

A Novel Solvent-free Room Temperature Molten Salt Electrolyte Based on LiODFB and 2-Oxazolidinone for EDLCs

Abstract A series of new room temperature molten salt electrolyte based on lithium oxalyldifluoroborate (LiODFB) and 2-Oxazolidinone (C3H5NO2, OZO) for EDLCs were synthesized by a facile and fast route. The investigation of the electrochemical characteristics of LiODFB-OZO molten salt electrolytes and the evaluation of LiODFB-OZO complex as electrolyte for EDLCs shows that the resulting molten salt exhibits excellent thermal stability, high ionic conductivity (up to ∼ 12.8 mS cm –1), a wide electrochemical stability window (∼ 3.8 V) and lower electron-transfer resistance (∼ 4.8 Ω).The EDLCs with the LiODFB-OZO complex electrolyte can be charged up to 3.0 V. At 30°C the EDLCs with LiODFB-OZO complex electrolyte based on activated carbon electrodes deliver a stable specific capacitance of ∼ 83.9 F g –1; At 70°C, they can deliver stable capacities of up to ∼ 106.1 F g –1 (current density, 1 mA cm –2). It is reasonable to assume that LiODFB-OZO complex system has some advantages as electrolyte for EDLCs with high energy density and high-power density, especially at elevated temperatures.

Effect of SiO2 Additive in Catalyst Layer and Electrolyte On the Performance for Mesothermal Fuel Cell Using Room Temperature Molten Salts

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Effect of SiO2 Additive in Catalyst Layer and Electrolyte on the Performance for Mesothermal Fuel Cell Using Room Temperature Molten Salts

Solid acid additive such as SiO2 to a room temperature molten salts (RTMs) applied membrane, which is a mesothermal fuel cell electrolyte without humidification, improves ionic conductivity and compression strength. However, the effect of SiO2 additive on the performance of the PEFCs is not yet clarified. In this study, we determined effect of SiO2 additive for membrane and catalyst layer on the performance of the PEFCs using diethylmethylammonium trifluoromethanesulfonate ([dema][TfO])/sulfonated polyimide (SPI) electrolytes to evaluate RTMS/SPI/solid acid system for PEFCs. The addition of SiO2 in the membrane and anode catalyst layer improved cell activity of catalyst layer, ionic conductivity and stabilize the cell performance against gas flow rate increase.These effects would be affected by the behavior of produced water.

Ionic, Organic and Strong Electrolytes with Graphene on Metal Oxide Composite Electrodes for Supercapacitors

This paper reports a scalable prototype supercapacitor using metal oxides and graphene oxide and an ionic liquid electrolyte. Our novel approach to combining pseudocapacitance and electric double layer capacitance in a tri-layered composite, promises to increase the energy density of the device, without sacrificing the high power density attributed to it. Solutions of KOH, Acetonitrile and 1-Ethyl-3-methylimidazolium tetrafluoroborate (EMIm-BF4) are used in manufacturing our devices, with more focus on the ionic liquid. These room temperature molten salts are predicted to function better as an electrolyte under extremely low temperatures. This paper presents the scalable synthesis of composites of reduced graphene oxide on MnO2 nanowires and Co3O4 nanorods. We assemble the devices with different electrolytes and employ a modified electrophoretic deposition process which produces uniform layers of rGO on semiconductors, metals and flexible substrates.

Ionic Conductivity of [dema][TfO]/Solid Acid-Base Composite Membrane

Solid acids or bases are expected to improve an ionic conductivity and mechanical properties of the novel proton conductive electrolyte using diethylmethylammonium trifuluoromethane-sulfonate ([dema][TfO]) of a room temperature molten salt (RTMS). In our previous study, SiO2 as a solid acid and MgO as a solid base have positive interaction with [dema][TfO] for the ionic conductivity. In this study, the effect of SiO2 or MgO addition into the ion gel membrane which is the mixture of a polymer and the RTMS on the ionic conductivity has been investigated. The results show that addition of a solid acid or base to the membrane improves compression strength, wettability of the RTMS and mechanical properties. Moreover, the SiO2 complex membrane improve the ionic conductivity because of the positive interaction at SiO2 /[dema][TfO] interfaces.

Development of Highly-Sensitive Electrochemical Measurement System on Dry Chemistry Using Ionic Liquid

It is necessary to detect some disease marker molecules in body fluid in order to find out the disease in an early stage. Most of conventional chemical sensors seem to have problems in terms of sensitivity. We have focused on substitutional stripping voltammetry (SSV), which is highly-sensitive electrochemical measurement technique and been developing a sensor. However, it is impossible for conventional SSV to be applied for sensor without any treatment due to the complexities that SSV requires salt bridge and two electrochemical cells. Hydrophobic ionic liquid which is room-temperature molten salt was mixed with polymer. The obtained gel possessed ionic conductivity, and could replace the auxiliary electrolyte solution and the salt bridge for SSV. We have succeeded to conduct SSV in a simplified system by use of the gel.

A Silicon‐based Imidazolium Ionic Liquid Iodide Source for Dye‐Sensitized Solar Cells

AbstractRoom temperature molten salt 1‐methyl‐3‐(trimethylsilyl)methyl‐imidazolium iodide (MSII) was used for iodide sources in dye‐sensitized solar cells with an organic sensitizer 2‐cyano‐3‐[5‐[4‐[3‐[4‐(4‐(N,N‐bis(4‐methoxyphenyl)amino)phenyl)phenyl]‐2,5‐di‐n‐butyl‐pyrrolo[3,4‐c]pyrrole‐1,4‐dione]phenyl]furan‐2‐yl] acrylic acid (DPP‐I) as light harvester. With an optimized electrolyte (MSII:I2:BI:GuNCS24:2:2:0.4, BI and GuCNS are short for benzimidazole and guanidine thiocyanate, respectively), photovoltaic parameters (Jsc, Voc, and ff) of device are 8.97 mA·cm−2, 600 mV and 0.61, respectively, yielding a maximum overall photo‐to‐energy conversion ef?ciency (η) of 3.23%. And then the charge‐transfer mechanism of devices was deeply analyzed with electrochemical impedance spectroscopy (EIS) in the dark.

A Review of Ionic Liquid Lubricants

Due to ever increasing demands on lubricants, such as increased service intervals, reduced volumes and reduced emissions, there is a need to develop new lubricants and improved wear additives. Ionic liquids (ILs) are room temperature molten salts that have recently been shown to offer many advantages in this area. The application of ILs as lubricants in a diverse range of systems has found that these materials can show remarkable protection against wear and significantly reduce friction in the neat state. Recently, some researchers have shown that a small family of ILs can also be incorporated into non-polar base oils, replacing traditional anti-wear additives, with excellent performance of the neat IL being maintained. ILs consist of large asymmetrical ions that may readily adsorb onto a metal surface and produce a thin, protective film under boundary lubrication conditions. Under extreme pressure conditions, certain IL compounds can also react to form a protective tribofilm, in particular when fluorine, phosphorus or boron atoms are present in the constituent ions.

Flow visualization and velocity measurement in a small-scale open channel using an electron microscope

The present note describes a method for use in conjunction with a scanning electron microscope (SEM) that has been developed to visualize a liquid flow under a high-level vacuum and to measure a velocity field in a small-scale flow through an open channel. In general, liquid cannot be observed via a SEM, because liquid evaporates under the high-vacuum environment of the SEM. As such, ionic liquid and room temperature molten salt having a vapor pressure of nearly zero is used in the present study. We use ionic liquid containing Au-coated tracer particles to visualize a small-scale flow under a SEM. Furthermore, the velocity distribution in the open channel is obtained by particle tracking velocimetry measurement and a parabolic profile is confirmed.

Ionic liquid polymer electrolytes

Ionic liquids (ILs) are room-temperature molten salts that possess unique properties, such as negligible vapour pressure, good thermal stability and non-flammability, together with high ionic conductivity and a wide window of electrochemical stability. Combining ILs with polymer electrolytes offers the prospect of new applications e.g. in batteries and fuel cells, where they surpass the performance of conventional media such as organic solvents (in batteries) or water (in polymer electrolyte membrane fuel cells), giving advantages in terms of improved safety and a higher operating temperature range. However, the most important challenge is how to immobilize ILs in polymer matrices while retaining their sought-after properties. Our goal in this review is to survey the recent developments and issues within IL research in polymer electrolytes.

Conductivity and viscosity properties of associated ionic liquids phosphonium orthoborates

A new group of room temperature molten salts based on asymmetric isobutyl(trihexyl)phosphonium cation with different chelated orthoborate anions are presented in this report. The physicochemical properties of these compounds as glass transition temperature, thermal stability, viscosity and conductivity are determined and discussed on structural basis. The highest room temperature conductivity observed was for the isobutyl(trihexyl)phosphonium bis(malonate)borate. The results indicate that the prepared orthoborates have lower viscosities, better conductivities when compared to their precursor, isobutyl(trihexyl)phosphonium bromide. Our investigation has found that those new compounds have an intermediate-to-fragile behavior. We plotted the conductivity and viscosity data according to Walden's rule and found that they can be classified as an associated ionic liquid (AIL) an intermediate between a true ionic liquid and a molecular species.

The role of upstream distal electrodes in mitigating electrochemical degradation of ionic liquid ion sources

Ionic liquid ion sources produce molecular ions from micro-tip emitters wetted with room-temperature molten salts. When a single ion polarity is extracted, counterions accumulate and generate electrochemical reactions that limit the source lifetime. The dynamics of double layer formation are reviewed and distal electrode contacts are introduced to resolve detrimental electrochemical decomposition effects at the micro-tip apex. By having the emitter follow the ionic liquid potential, operation can be achieved for an extended period of time with no apparent degradation of the material, indicating that electrochemistry can be curtailed and isolated to the upstream distal electrode.

Simulation of the Properties of 1-Ethyl-3-Methyl-Imidazolium Chloride/Chloroaluminate Ionic Liquids: Concentration and Temperature Dependence

Influences of the molar fractions of AlCl3and temperature on room temperature molten salts 1-ethyl-3-methyl-imidazolium Chloride /Chloroaluminate [Emim]Cl/AlCl3are studied by molecular dynamics simulation. The physical and chemical properties such as density, diffusion coefficients, viscosity, conductivity of [Emim]Cl/AlCl3with different molar fraction of AlCl3are calculated. The density is obtained as 1.1744g/cm3for [Emim]Cl, which agree well with the experimental value (1.186g/cm3). It was shown that the density and conductivity increase, whereas the viscosity decreases with the increasing of molar fraction of AlCl3. The self-diffusion coefficients of [Emim]+, Cl-and AlCl3increases and the changes of self-diffusion coefficient of AlCl3is the biggest as to molar fraction increase. It is shown that the conductivity, the self-diffusion coefficient of particles all increase, and the changes of AlCl3is the biggest with the increasing of temperature, whereas the density and viscosity reduce.

Simulation of the Properties of 1-Ethyl-3-Methyl-Imidazolium Chloride/Chloroaluminate Ionic Liquids: Concentration and Temperature Dependence

Influences of the molar fractions of AlCl3 and temperature on room temperature molten salts 1-ethyl-3-methyl-imidazolium Chloride /Chloroaluminate [Emim]Cl/AlCl3 are studied by molecular dynamics simulation. The physical and chemical properties such as density, diffusion coefficients, viscosity, conductivity of [Emim]Cl/AlCl3 with different molar fraction of AlCl3 are calculated. The density is obtained as 1.1744g/cm3 for [Emim]Cl, which agree well with the experimental value (1.186g/cm3 ). It was shown that the density and conductivity increase, whereas the viscosity decreases with the increasing of molar fraction of AlCl3. The self-diffusion coefficients of [Emim]+, Cl- and AlCl3 increases and the changes of self-diffusion coefficient of AlCl3 is the biggest as to molar fraction increase. It is shown that the conductivity, the self-diffusion coefficient of particles all increase, and the changes of AlCl3 is the biggest with the increasing of temperature, whereas the density and viscosity reduce.

Simulation of the Structure and Properties of Room Temperature Molten Salts 1-Ethyl-3-Methyl-Imidazolium Chloride/Chloroaluminate

Molecular dynamics simulation method is used to study the [Emim]Cl ionic liquid at the 300K. The density is obtained as 1.1744g/cm3 which agree well with the experimental value (1.186g/cm3) and the relative deviation is only 0.9%. The microstructure, dynamics, and physical chemical properties such as radial distribution functions, diffusion coefficients, viscosity, conductivity of room temperature molten salts [Emim]Cl/AlCl3 with different molar fraction of AlCl3 are calculated. It is shown that the density and electrical conductivity increase, whereas the viscosity decreases with the increasing of molar fraction of AlCl3. The self-diffusion coefficients of [Emim]+, Cl- and AlCl3 increases and the changes of self-diffusion coefficient of AlCl3 is the biggest as to molar fraction increase.

The effects of functional ionic liquid on properties of solid polymer electrolyte

Polyethylene oxide (PEO) based solid state electrolytes have been thought as promising electrolytes to replace the organic liquid electrolyte for lithium ion batteries. But the lower ionic conductivities at room temperature restrict their application. In this paper, functional ionic liquid and polymer mixed electrolytes are prepared from N-methyoxymethyl- N-methylpiperidinium bis(trifluoromethanesulfonyl)imide (PP1.1O1TFSI) and polyethylene oxide. The PP1.1O1TFSI, a kind of room-temperature molten salt, was added to the conventional P(EO) 20LiTFSI polymer electrolyte and resulted in a significant improvement of the ionic conductivity at room temperature. LiFePO 4/Li and Li 4Ti 5O 12/Li cells using this kind of electrolyte show high reversible capacity and stable cycle performance.