Room Temperature Molten Salt Electrolyte Research Articles

A High Rate and Stable Hybrid Li/Na-Ion Battery Based on a Hydrated Molten Inorganic Salt Electrolyte.

Taking into the consideration safety, environmental impact, and economic issue, the construction of aqueous batteries based on aqueous electrolyte has become an indispensable technical option for large-scale electrical energy storage. The narrow electrochemical window is the main problem of conventional aqueous electrolyte. Here, an economical room-temperature inorganic hydrated molten salt (RTMS) electrolyte with a large electrochemical stability window of 3.1V is proposed. Compared with organic fluorinated molten salts, RTMS is composed of lithium nitrate hydrate and sodium nitrate with much lower cost. Based on the RTMS electrolyte, a hybrid Li/Na-ion full battery is fabricated from cobalt hexacyanoferrate cathode (NaCoHCF) and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) anode. The full cell with the RTMS electrolyte exhibits a fantastic performance with high capacity of 139 mAh g-1 at 1 C, 90 mAh g-1 at 20 C, and capacity retention of 94.7% over 500 cycles at 3 C. The excellent performances are contributed to the unique properties of RTMS with a large electrochemical window, solvated H2 O free and high mobility of Li+ , which exhibits excellent Li-ions insertion and extraction capacity of NaCoHCF. This RTMS cell provides a new economic choice for large-scale energy storage.

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.

A Novel Room Temperature Molten Salt Electrolyte Based on LiBOB and 2-Oxazolidinone for Electrochemical Capacitors

Abstract In this paper, a novel room temperature molten salt electrolyte based on lithium bis(oxalato)borate (LiB(C2O4)2, LiBOB) and 2-Oxazolidinone (C3H5NO2, OZO) has been prepared as the electrolyte of electrochemical capacitors (EDLCs). The conductivity, thermal stability and electrochemical stability of the LiBOB-OZO electrolytes are investigated. It shows excellent thermal stability, high ionic conductivity (up to 10.4mS cm−1) and a wide electrochemical stability window (4.5 V). The temperature dependence of conductivity for the electrolytes follows the VFT equation, which demonstrates a solvent-assisted ionic conductivity mechanism. Based on it, a specific recipe of the LiBOB-OZO electrolytes (with a molar ratio of 1:6) is evaluated by cylic voltammetry, AC impedance spectroscopy, and galvanostatic charging-discharging in a test EDLC capacitor. It is found that the EDLC with the LiBOB-OZO complex electrolyte can be charged up to 2.5 V, the specific capacitance based on an activated carbon electrode can reach 92.5 F g−1 at 50°C, the equivalent series resistance (ESR) decreases sharply from 18.2 Ω at 30 °C to 7.2 Ω at 70 °C. Then, an EDLC of higher energy density and power density can be obtained，especially in the temperatures above 50 °C

A Novel Solvent-free Electrolyte Based on LiBOB and Acetamide for Electrochemical Capacitors

Abstract Room temperature molten salts or ionic liquids are promising “solvent-free” electrolytes for high-voltage double layer supercapacitors. In this work, a novel binary room temperature molten salt electrolyte based on LiBOB and acetamide has been prepared. The electrolyte shows excellent thermal stability, high ionic conductivity and a wide electrochemical stability window, especially at higher temperatures. The temperature dependence of conductivity for the electrolytes follows the VFT equation, which demonstrates a solvent-assisted ionic conductivity mechanism. The EDLC with the LiBOB-acetamide complex electrolyte at molar ratio of 1:6 can be charged up to 2.5 V with better rate performance. The specific capacitance based on activated carbon electrodes can reach 103.1 F g−1. It is reasonable to assume that LiBOB-acetamide complex system has advantages as electrolyte for EDLCs with high energy density.

Electrodeposition of Zinc from Binary ZnCl2-DMSO2 Molten Electrolyte at Room Temperature

The electrochemical behaviour of zinc on copper, platinum, and tungsten working electrodes was investigated in a binary ZnCl2-DMSO2 room temperature molten salt electrolyte in the temperature range of 60 - 80◦C. Various over-potentials, −0.1, −0.2, −0.3, −0.4, and −0.5 V, were chosen as deposition potentials. The nucleation/growth of zinc changed from progressive to instantaneous if the over-potentials increased from low to high level. The surface morphology and crystal structure of the deposited layer were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Moreover, larger grain size and hexagonal close packing of the zinc layer at −0.5 V were observed by transmission electron microscopy (TEM) with electron diffraction mapping.

Physical and electrochemical properties of new binary room-temperature molten salt electrolyte based on LiBETI and acetamide

A new binary room-temperature molten salt electrolyte based on lithium bis(perfluoroethysulfonyl) imide (LiN(SO 2C 2F 5) 2, LiBETI) and acetamide has been prepared and characterized by differential scanning calorimetry (DSC), IR, Raman spectroscopy, ac impedance, and cyclic voltammetry, etc. Both LiBETI and acetamide are solid, but their mixture is a liquid at room temperature with a eutectic temperature of −57 °C at a molar ratio of 1:4. The formation of this new room-temperature molten salt (RTMS) is due to strong interaction between the two components, as confirmed by IR and Raman spectroscopy. The conductivity behaviour consists with the VTF equation. The ionic conductivity of LiBETI/acetamide complex at a molar ratio of 1:6 reaches 1.27×10 −3 S/cm at 30 °C, much higher than 4.06×10 −4 S/cm of another similar system of LiTFSI/urea system reported by us previously. The reduction and oxidation potentials of this RTMS were observed at 0.6 and 3.8 V vs. Li/Li +, respectively.

Ionic Conductivity and Association Studies of Novel RTMS Electrolyte Based on LiTFSI and Acetamide

A novel room-temperature molten salt (RTMS) electrolyte based on lithium bis(trifluoromethane sulfone) imide LiTFSI] and acetamide has been prepared and investigated by ac impedance, nuclear magnetic resonance (NMR), Fourier transform infrared, and Raman spectroscopy. The ionic conductivity of the complex for reaches at 25°C and rises to at 60°C. The behavior of ion transport obeys well the empirical Vogel-Tamman-Fulcher type relationship for the RTMS electrolyte. Strong cation-solvent interaction has been clarified by the variation of NMR chemical shifts and the spectral evolution of the group in the complex system. The effect of salt concentration and temperature upon the ionic association has also been investigated. It is found that ionic association increases with the increases of salt concentration and temperature in the RTMS electrolyte. © 2004 The Electrochemical Society. All rights reserved.

Electrochemical in situ STM study of Al and Ti–Al alloy electrodeposition on Au(111) from a room temperature molten salt electrolyte

The electrodeposition of Al and Ti–Al alloys on Au(111) from an acidic aluminium chloride-1-methyl-3-butylimidazolium chloride (AlCl3–MBImC) room-temperature molten salt electrolyte containing TiCl4 was studied by cyclic voltammetry and chronoamperometry and in particular, nucleation and growth processes were monitored in situ by means of electrochemical scanning tunneling microscopy (EC-STM) for the first time. Two underpotential deposition (UPD) states for Al were observed in the cyclic voltammogram at 0.51 and +0.22 V vs. Al/Al3+. At corresponding UPD conditions STM images show different nucleation behavior for Al: first a growth of clusters all over the Au surface, and later preferentially along the step edges leading to a step edge decoration. Potential step experiments imply progressive nucleation and growth and are evidenced by STM images obtained at different time intervals showing the growth of Al clusters of up to 8 nm diameter in size. After anodic dissolution of the deposited Al film, the appearance of circular holes of a size comparable with the Al clusters notably along Au step edges indicates Al–Au surface alloy formation. Tunneling current vs. bias voltage (I–U) curves of the Al clusters exhibit a reduced tunneling barrier height (Φ) of 0.23 eV. A distinct two-dimensional nucleation of Ti–Al clusters begins to occur at 0.5 V vs. Al/Al3+ exclusively on the Au terraces. They grow in the form of chains reaching a size of about 2–3 nm diameter in size, smaller in comparison with Al clusters. X-Ray photoelectron spectra of the potentiostatically deposited film under overpotential deposition (OPD) conditions confirm the formation of a Ti–Al alloy phase.

Novel room temperature molten salt electrolyte based on LiTFSI and acetamide for lithium batteries

A novel room temperature molten salt (RTMS) electrolyte composed of lithium bis(trifluoromethane sulfone)imide (LiN(SO 2CF 3) 2, LiTFSI) and acetamide was found. Both LiTFSI and acetamide are solid at room temperature, but their mixture is a liquid at room temperature with a eutectic temperature of −67 °C at a molar ratio of 1:4 (LiTFSI:Acetamide). The room temperature ionic conductivities of some compositions of the RTMS exceed 10 −3 S/cm. The oxidation and reduction potentials of this RTMS electrolyte were observed at 4.4 and 0.7 V versus Li/Li +, respectively. In addition, a Li/RTMS/MnO 2 test cell was constructed and tested using the above mentioned RTMS electrolyte. Due to its superior physicochemical properties, it can be suggested potential applications as lithium battery electrolytes.

New Binary Room-Temperature Molten Salt Electrolyte Based on Urea and LiTFSI

A novel room-temperature molten salt electrolyte based on urea and lithium bis(trifluoromethane sulfone)imide (LiN(SO2CF3)2, LiTFSI) has been synthesized and characterized by differential scanning ...

In situ STM and STS study of Ni xAl 1− x alloy formation on Au(1 1 1) by electrodeposition from a molten salt electrolyte

The electrodeposition of Ni, Ni x Al 1− x alloys and Al from the Lewis acid room temperature molten salt electrolyte AlCl 3/1-methyl-3-butylimidazolium chloride on Au(1 1 1) has been studied by STM and voltage tunneling spectroscopy. Layer by layer growth of Ni starts already in the underpotential range, while below the equilibrium potential a columnar growth of 3D Ni clusters along the step edges is observed. At potentials below −0.2 V vs Ni/Ni(II) the complete Au surface is covered with a 3D deposit due to Ni and Al codeposition. The tunnel barriers φ, which were determined at the electrode/electrolyte interface, exhibit qualitatively the same relative reduction as for the vacuum interface.

The Application of Room Temperature Molten Salt with Low Viscosity to the Electrolyte for Dye-Sensitized Solar Cell

Abstract The effect of the viscosity of room temperature molten salt (RTMS) electrolyte has been investigated on the performance of dye-sensitized solar cell (DSSC). Both the short circuit photocurrent and conversion efficiency are increased with decreasing the viscosity of RTMS as in the case of conventional electrolytes. The conversion efficiency of 2.1% observed for the cell of EMIm-F·2.3HF is the highest value reported for all the DSSC consisted of RTMS.

Studies on the Components of Aluminum Nagative Electrode for the Secondary Batteries with Room Temperature Molten Salt Electrolyte

Studies on the Components of Aluminum Nagative Electrode for the Secondary Batteries with Room Temperature Molten Salt Electrolyte

Voltammetry and Conductivity of a Polyether‐Pyridinium Room Temperature Molten Salt Electrolyte and of Its Polymer Electrolyte Solutions in Polydimethylsiloxane

This report describes the synthesis, microelectrode voltammetry, and ionic conductivity of a new room temperature molten salt N‐(methoxy(ethoxy)2ethyl)pyridinium p‐toluenesulfonate (abbreviated as ) and of its solution in a hydroxy‐terminated polydimethylsiloxane. Both ionically conductive liquids exhibit voltammetric potential windows of about 1.5 V. The negative potential limit is determined by the reduction of the pyridinium species, with subsequent radical coupling to form a voltammetrically observed viologen dimer. The estimated diffusivities of the species, of a diethyleneglycol‐tailed ferrocene redox solute studied, and by application of Nernst‐Einstein relation to the ionic charge carriers, all lie in the to range. Viscosities and glass transition thermal observations are reported as is the fit of the temperature dependencies of ionic conductivity in and in mixtures to Vogel‐Tamman‐Fulcher predictions.

Copper Deposition from Cu(I) Ions in CuCl-BPC Molten Salts - Microstructural Analysis of the Melts

The characteristics of a CuCl-BPC room-temperature molten salt electrolyte and the morphology of the Cu deposits are strongly dependent on CuCl content. It has been assumed that these changes are affected by the ionic species in the melt. Molar fractions of the ionic species were calculated by the simulation method, and their structures computed by ab initio molecular orbital method. The structure deduced from neutron diffraction measurements are consistent with the calculated results.

Electrochemical insertion of lithium, sodium, and magnesium in molybdenum(VI) oxide

The electrochemical insertion of divalent magnesium cations into orthorhombic molybdenum(VI) oxide was studied with regard to their use as electroactive species in ion-transfer battery systems and compared to the insertion of Li + and Na +. Specific charges of up to 300 and 240 Ah kg −1 were obtained in organic, propylene carbonate-based electrolytes for the lithium and sodium insertion, respectively, in the first reduction half-cycle. Reversible Mg 2+ insertion could be demonstrated in a room temperature molten salt electrolyte consisting of 3 wt.% MgCl 2, 41 wt.% 1-ethyl-3-methylimidazolium chloride, and 56 wt.% AlCl 3. Specific charges of up to 160 Ah kg −1 were obtained with MoO 3 in the first reduction half-cycle. The Mg 2+ insertion process can be enhanced using an organic electrolyte with traces of H 2O. In 1 M Mg(ClO 4) 2/acetonitrile with 3 mol% of H 2O, specific charges of up to 210 Ah kg −1 were measured in the first reduction.

常温型溶融塩電解浴を用いた電気Ａｌめっき

常温型溶融塩電解浴を用いた電気Ａｌめっき

An Aluminum/Chlorine Rechargeable Cell Employing a Room Temperature Molten Salt Electrolyte

A novel rechargeable electrochemical cell is described which employs an Al negative and graphite positive electrode in a room temperature molten salt electrolyte of 1.5:1 . The graphite positive electrode functions as a reversible intercalation electrode for chlorine, eliminating the need for separate anolyte and catholyte compartments. The cell possesses an average discharge voltage of 1.7V for currents of 1–10 mA/g graphite and over 150 cycles at 100% depth‐of‐discharge for positive electrode limited cells have been demonstrated. Improvements in the chlorine storage capacity of the positive electrode are needed to obtain satisfactory energy densities.

Mechanisms of Charge Transfer at the n ‐ GaAs / Room Temperature Molten Salt Electrolyte Interface

Photoelectrochemical (PEC) characterization was carried out on electrodes in contact with a room temperature molten salt electrolyte comprising mixtures of and n‐butyl pyridinium chloride (BPC) in varying molar ratios. The ferrocene/ferricenium ion couple was used as the redox system in these studies. The barrier height for charge transfer, which determines the ultimate efficiency of any photovoltaic system, was determined from dark current‐voltage measurements. These data were in good agreement with previously determined values from capacitance measurements. The residual barrier heights in the illuminated PEC system were determined from open‐circuit voltage and short‐circuit current densities using Schottky barrier theory. A simple method for estimating the reorganization energy (λ) of a redox system from dark current‐voltage measurements is presented. A value of was thus deduced for the ferrocene/ferricenium ion couple in the electrolyte. The acidic electrolyte showed larger dark currents and inferior photoresponse relative to the case of electrodes in contact with basic electrolytes. Using the measured values of λ and the semiconductor bandedges, energy band diagrams were developed for the present PEC system as a function of electrolyte composition. The direct correlation which was seen between PEC performance and electrolyte composition is rationalized on the basis of these diagrams. The larger dark currents in the acid electrolytes were shown to result from greater overlap of the empty redox levels with the conduction bandedge in . On the other hand, in basic electrolyte systems, the filled redox levels overlap better with the valence bandedge leading to more efficient charge transfer on illumination. The role of surface states in mediating charge transfer and degrading PEC performance is discussed in this regard. A key finding of the present work is that the electrical behavior of semiconductor/electrolyte junctions is well described by Schottky barrier theory once the differences in the energy distribution in metals vis‐à‐vis electrolytes, are rationalized.

Effect of Temperature on the Operation of a Photoelectrochemical Device: Studies on the n ‐ GaAs / Room Temperature Molten Salt Electrolyte Interface

The effect of temperature on the photovoltaic performance of a photo‐electrochemical (PEC) system was evaluated by measurements on a model system comprising the pyridinium chloride (BPC)|carbon cell containing the ferrocene/ferricenium ion couple. Changes in the solar cell parameters for this system with temperature were monitored for the range from ambient to 85°C. The short‐circuit current densities showed a systematic increase over the temperature range while the open‐circuit voltage and fill‐factor (FF) showed a linear decrease at the rate of 3.6 mV/°C and 0.001/°C, respectively. The energy conversion efficiency (η) of the device showed a maximum at an intermediate temperature (∼50°C) beyond which the decline in and FFoutweighed the beneficial effect of temperature on , leading to a rapid fall‐off in η at temperatures above ∼60°C. The linear decrease of with increasing temperature was seen to be directly related to the increased dark current density at elevated temperatures. Analysis of the dark currentvs. voltage data by Schottky diode theory revealed the expected exponential dependence of the reverse saturation current density on temperature for the model PEC system. Measurement of the semiconductor flatband potential for the interface at varying temperatures revealed a further origin for the increase in dark currents with temperature. The shift in to positive potentials with increasing temperature reduced the effective activation energy (or barrier height) for electron injection from the electrolyte into the semiconductor in the dark. These results are discussed in terms of two mechanisms: (i) direct charge transfer between the semiconductor and the occupied redox levels in the electrolyte and (ii) electron injection into the semiconductor mediated by trap levels in the energy bandgap of the semiconductor. Finally, the effect of temperature on the Schottky diode parameters of the , cell is discussed in terms of enhanced surface and bulk carrier recombination effects at elevated temperatures. These lead to the observed deterioration in the fill‐factor because of the increased series resistance associated with recombination‐generation current flow paths.