Propylene Carbonate Solution Research Articles

Potential-Controlled Boundary Lubrication of Stainless Steels in Non-aqueous Sodium Dodecyl Sulfate Solutions

In aqueous solutions, sodium dodecyl sulfate (SDS) surfactant can form a boundary film on metal surfaces to provide lubrication for sliding surfaces in contact. Previous studies have demonstrated that the boundary lubrication of SDS film can be inhibited or enhanced substantially by changing the surface potential of the rubbing metal surfaces. In this study, the SDS surfactant was added to a non-aqueous base fluid, propylene carbonate (PC), and the boundary lubrication behaviors of the solution for stainless steels were investigated under different potential conditions. Friction measurement, electrochemical impedance spectroscopy, cyclic voltammetry, and electrochemical quartz crystal microbalance techniques were employed to investigate the lubricating performance and adsorption film of the sodium dodecyl sulfate (SDS) film on two kinds of steels (AISI 316L, AISI 440C) in propylene carbonate (PC) solution. Similar to aqueous SDS solutions, the lubricating performance of the SDS/PC solution depends upon the electrode potential within the potential range from −1.5 to +1.5 V versus Ag/AgCl, which suggests the potential-dependent reversible change in the adsorbed film. When the potential is positive, both friction and wear of the tested stainless steels are relatively lower due to the presence of the adsorbed SDS film. As the potential is shifted to the negative regime, the DS chains in the adsorbed film are replaced by the PC molecules gradually, and friction coefficient increases by 100 % or more, depending on the load condition and the hardness of the stainless steels.

Competition of Desolvation and Stabilization of Organic Electrolytes in Extremely Narrow Nanopores

Organic electrolytes are widely used for electric double-layer capacitors. However, the molecular mechanism involved is far from being understood. We demonstrate the structures and stabilities of tetraethylammonium and tetrafluoroborate ions in propylene carbonate solution in carbon nanopores using Monte Carlo simulations. These ions were significantly desolvated at nanopore widths below 1.0 nm. The nanopore potential compensated for the loss of stability of the ions as a result of desolvation for nanopore widths of 0.7–1.2 nm for Et4N+ and 0.6–0.9 nm for BF4–. High-capacitance electrodes can therefore be obtained using such nanoporous carbons.

Activated carbon–carbon nanotube nanocomposite coatings for supercapacitor applications

Electrochemical double layer capacitor cells were fabricated based on electrodes with activated carbon (AC) coating as the host material, targeting large energy storage. Highly dispersed multiwall carbon nanotubes (MWNTs) were added to form nanocomposite coatings, used as electrodes targeting high-power performance for very low content of MWNTs. 1M tetraethylammonium tetrafluoroborate–propylene carbonate solution was used as organic electrolyte. The resulting cells were characterized using impedance spectroscopy, cyclic voltammetry, and galvanostatic charge–discharge tests. It was concluded that at optimum composition of AC–MWNT coatings both power and energy densities are raised whereas further increase of the MWNT content would increase the power density but decrease the energy density.

Electrochemical characteristics of propylene carbonate solutions of tetraethylammonium tetrafluoroborate

The specific and molar electric conductivities of propylene carbonate solutions of Et4NBF4 with concentrations of 0.15–1.4 m were determined at 283.15, 298.15, and 313.15 K. The temperature dependence of the electric conductivity of the system was analyzed. The concentration dependence of electric conductivity was described in terms of the Castell-Amis equation. A comparative analysis of the charge transfer in Et4NBF4 and LiAsF6 systems in propylene carbonate was performed using the concept of quasicrystallinity of concentrated electrolyte solutions. The range of potentials in which the electrolyte solutions are stable on a platinum electrode was determined.

리튬 덴드라이트의 성장 반응에 미치는 공용매의 영향

Abstract >> This study examined the electrochemical deposition and dissolution of lithium on nickel electrodesin 1 mol dm -3 (M) LiPF 6 dissolved in propylene carbonate (PC) containing different 1,2-dimethoxyethane (DME)concentrations as a co-solvent. The DME concentration was found to have a significant effect on the reactions occurring at the electrode. The poor cycleability of the electrodes in the pure PC solution was improved considerablyby adding small amounts of DME. This results suggested that the dendritic lithium growth could be suppressedby using co-solvents. After hundredth cycling in the 1 M LiPF 6 / PC:DME (67:33) solution, almost no dead lithiumhas been found from the disassembled cell, resulting from suppression of dendritic lithium growth. Scanning electronmicroscopy revealed that dendritic lithium formation was greatly affected by the ratio of DME. Raman spectroscopyresults suggested that the structure of solvated lithium ions is a crucial important factor in suppressing dendriticlithium formation.Key words : Dendritic lithium(리튬 덴드라이트), Co-solvent(공용매), Solvation structure(용매화 구조), Solvationnumber(용매화 수), Interfacial reaction(계면 반응), Negative electrode(음극)

Electrolytic Characteristics of Tetramethylammonium Compounds and Performance of Electric Double-Layer Capacitors Evaluated by Using Transmission-Line Model

The use of oxalatoborate ions, difluoro(oxalato)borate (DFOB−) and bis(oxalato)borate (BOB−), improved the solubility of the tetramethylammonium compounds in propylene carbonate (PC) and increased the capacitances of electric double-layer capacitors (EDLCs). Ionic conductivities of tetramethylammonium difluoro(oxalato)borate (TMADFOB) solutions in PC were slightly lower than that of tetraethylammonium tetrafluoroborate (TEABF4) solutions. However, the conductivities were higher than those of tetramethylammonium bis(oxalato)borate (TMABOB) and tetraethylammonium bis(oxalato)borate (TEABOB) solutions. We have used a transmission-line network of finite length as the equivalent circuit of the average pore of an activated carbon electrode. The equation we derived has enough flexibility to show the effect of double-layer capacitance on the length and shape of a single pore. We evaluated the performance of EDLCs by comparing the theoretical and the experimental discharge curves. The TMADFOB solution in PC afforded the highest capacitance.

New lithium-conducting gel electrolytes containing superbranched polymers

New polymer gel electrolytes containing superbranched polymers were developed. The gel electrolyte containing 20 wt % superbranched polymer, 6 wt % methylmethacrylate, 4 wt % triethyleneglycol dimethacrylate, and 70 wt % 1 M propylene carbonate solution of LiClO4 was found to have a maximum conductivity of ∼9 × 10−4 S/cm at room temperature and an effective activation energy of conductivity of 18 kJ/mol. The physicochemical properties of the gel electrolyte were correlated with its composition using electrochemical impedance spectroscopy, thermomechanics, and differential scanning calorimetry. The glass-transition temperature of these electrolytes depended only on the liquid electrolyte content and decreased from −80 to −93°C when the concentration of 1 M LiClO4/PC increased from 60 to 80 wt %. As the content of the superbranched polymer increased from 0 to 20 wt % at positive temperatures, the modulus of elasticity decreased, while the conductivity increased. When the content of the superbranched polymer increased at the expense of the liquid electrolyte, the conductivity of the system decreased.

Carbon-fiber composites of organometallic intercalated polyaniline and polypyrrole doped with sodium polystyrene sulfonate as electrodes for lithium-ion batteries

Carbon fiber (CF) composites of organometallic intercalated polyaniline (Pani) and polypyrrole (Ppy) doped with polystyrene sulfonate (PSS) were electrochemically synthesized and tested as electrodes for lithium-ion batteries. From the results obtained by cyclic voltammetry, X-ray photoelectron spectroscopy, and energy-dispersive X-ray spectroscopy, it was concluded that the incorporation of copper(II) ions in the polymeric composite was successfully attained by adsorption of Cu2+ ions and 2,5-dimercapto-1,3,4-thiadiazole (DMcT) monomers on the carbon microfibers. The experimental electrochemical impedance response of the obtained Pani(DMcT–Cu ion)/CF composite was simulated by adequate equivalent electrical circuits. After 20 charge/discharge cycles, the experimental discharge specific capacity of the Pani(DMcT–Cu ion)/CF composite was 118 mA h g−1 (100% coulombic efficiency) using a 1 mol L−1 LiClO4 solution in propylene carbonate, and 110 mA h g−1 when a polymeric electrolyte was used. In the charge/discharge tests of the Ppy-PSS/Pani/CF composite as anode, a high discharge specific capacity of 225 mA h g−1 was obtained after 20 cycles. The resulting Ppy-PSS/Pani/CF/polymeric electrolyte/Pani(DMcT–Cu ion)/CF battery presented a specific capacity of 62 mA h g−1 and could be charged up to 2.0 V, yielding an energy density 425 W h g−1, with a coulombic efficiency of about 98%.

Excited-State Relaxation of Ruthenium Polypyridyl Compounds Relevant to Dye-Sensitized Solar Cells

Remarkably little is known about metal-to-ligand charge transfer (MLCT) excited-state relaxation pathways for the ruthenium polypyridyl compounds commonly utilized in dye-sensitized solar cells. Herein, we report variable-temperature photoluminescence studies of compounds of the general type cis-Ru(LL)2(X)2, where LL is a bipyridyl ligand and X is CN(-) or NCS(-), and contrast them with the well-known Ru(bpy)3(2+) and Os(bpy)3(2+), where bpy is 2,2'-bipyridine, to identify relaxation pathways. In fluid acetonitrile and propylene carbonate solutions, excited-state relaxation was found to obey a first-order kinetic model. An Arrhenius analysis revealed internal conversion to two different states, assigned to an upper MLCT excited state and a ligand field excited state. Relaxation through the upper MLCT excited state typically displayed pre-exponential factors of 10(7)-10(8) s(-1) with activation energies of 400-900 cm(-1), while relaxation rates through ligand field states occurred with 10(14)-10(15) s(-1) and activation energies of 4000-5000 cm(-1). Nonradiative decay through LF states was sensitive to the ligand identity, but in a manner that was not fully consistent with the spectrochemical series. Excited-state relaxation of cis-Ru(dcbH2)2(NCS)2, where dcbH2 is 4,4'-(CO2H)2-2,2'-bipyridine, sometimes termed N3, anchored to mesoporous TiO2 or ZrO2 thin films immersed in CH3CN occurred through the upper MLCT excited state with activational parameters in surprisingly good agreement with those abstracted from data measured in fluid solution. An important finding from these studies is that the population of dissociative ligand field excited states is unlikely to lead to unwanted photochemistry of dye-sensitized solar cells based on cis-Ru(LL)2(NCS)2-type compounds at room temperature.

Gel-combustion synthesis of LiFePO4/C composite with improved capacity retention in aerated aqueous electrolyte solution

The LiFePO4/C composite containing 13.4wt.% of carbon was synthesized by combustion of a metal salt–(glycine+malonic acid) gel, followed by an isothermal heat-treatment of combustion product at 750°C in reducing atmosphere. By a brief test in 1M LiClO4–propylene carbonate solution at a rate of C/10, the discharge capacity was proven to be equal to the theoretical one. In aqueous LiNO3 solution equilibrated with air, at a rate C/3, initial discharge capacity of 106mAhg−1 was measured, being among the highest ones observed for various Li-ion intercalation materials in aqueous solutions. In addition, significant prolongation of cycle life was achieved, illustrated by the fact that upon 120 charging/discharging cycles at various rates, the capacity remained as high as 80% of initial value. The chemical diffusion coefficient of lithium in this composite was measured by cyclic voltammetry. The obtained values were compared to the existing literature data, and the reasons of high scatter of reported values were considered.

Production of three certified reference materials for water content based on mixed solutions of butanol, xylene and propylene carbonate

Certified reference materials (CRMs) for water content with good accuracy and homogeneity are required for calibration or validation of the Karl Fischer titration and for establishing the traceability of water content results. Three such CRMs were produced and certified: GBW 13512, 13513 and 13514 are based on solvent mixtures consisting of butanol, xylene and propylene carbonate with water contents of 10.01, 1.067 and 0.139 mg/g, respectively, certified by the Karl Fischer coulometric and volumetric methods. These CRMs were prepared, dispensed and sealed under a humidity equal to the equilibrated humidity of their headspace. In this way, the between-bottle homogeneity uncertainty (u H,rel) could be kept as low as u H,rel = 0.12 % for GBW 13512. The certification methods, that is, Karl Fischer coulometric and volumetric methods, were calibrated using in-house water standards prepared by gravimetry. The results were traceable to the SI unit of mass. The relative deviation of the water contents between the two methods for GBW 13512 was only 0.05 %. The expanded uncertainty (U, k = 2) of three CRMs was 0.12, 0.024 and 0.012 mg/g, respectively. These CRMs for water content with good accuracy can be applied in the calibration or validation of measurement procedures to ensure accurate and comparable results.

Conductivity, viscosity and density of MClO4 (M = Li and Na) dissolved in propylene carbonate and γ-butyrolactone at high concentrations

The solution density, viscosity and conductivity of MClO4 (M = Li and Na) solutions in propylene carbonate and γ-butyrolactone are measured at the concentrations of <1.5–2.0 mol dm−3. The partial volume of the solute, derived from the density, of NaClO4 is greater than that of LiClO4 as expected. NaClO4 produces less viscous and more conductive solutions than LiClO4 throughout the examined concentration range. Notably, the conductivity of the NaClO4 solutions is 10–20% higher than that of the LiClO4 solutions at T/K = 298. The validity of the empirical cubic root law, Λ(C) = Λ0 − AC1/3, is examined, where Λ and Λ0 are the molar conductivities at the molarity C and at infinite dilution. The meaning of the slope A is interpreted in the theoretical framework of the pseudolattice model.

Two unsymmetrical lithium organoborates with mixed-ligand of croconato and oxalicdiolato or benzenediolato for lithium battery electrolytes

Two new unsymmetrical lithium salts, lithium (oxalicdiolato croconato)borate (LOCB) and lithium (1,2-benzene-diolato(2-)-o,o’ croconato)borate (LBDCB), are synthesized and characterized. The thermal characteristics of them, and their derivative, lithium bis(croconato)borate (LBCB), are examined by thermogravimetric analysis (TG). The thermal decomposition in air begins at 186 °C, 250 °C, and 265 °C for LBDCB, LBCB and LOCB, respectively. The order of the stability toward the oxidation of these organoborates is LBCB > LOCB > LBDCB. The cyclic voltammetry study shows that the LOCB and LBDCB solutions in propylene carbonate (PC) are stable up to 5.1 and 3.7 V versus Li+/Li. They are soluble in common organic solvents. Ionic dissociation properties of them are examined by conductivity measurements in PC, PC + ethyl methyl carbonate (EMC), PC + dimethyl ether (DME), PC + ethylene carbonate (EC)+ DME, PC + EC + EMC solutions. The conductivity values of the 0.10 mol dm−3 LOCB and LBDCB electrolytes in these solutions are lower than those of LBCB electrolytes.

Temperature Dependence of Self-Diffusion Coefficients of Ions and Solvents in Ethylene Carbonate, Propylene Carbonate, and Diethyl Carbonate Single Solutions and Ethylene Carbonate + Diethyl Carbonate Binary Solutions of LiPF6 Studied by NMR

The self-diffusion coefficients, D, of lithium, anions, and solvents in four binary-solution electrolytes of ethylene carbonate (EC)–diethyl carbonate (DEC) and three single-solution electrolytes of EC, DEC, and propylene carbonate (PC) including 1 M LiPF6 were measured by 1H, 7Li, and 19F NMR spectroscopy from (353 to 243) K or above freezing for seven solution electrolytes. In the single DEC electrolyte, DLi and DPF6 had almost the same values at every temperature, whereas DLi was smaller than DPF6 in the EC and PC solutions. In the binary EC–DEC electrolytes, as the ratio of EC increased, DLi gradually became smaller, while DPF6 remained almost unchanged in the temperature range studied. At 303 K, the degree of ion dissociation α was evaluated from the ionic conductivity, DLi and DPF6. The α value increased from 0.17 to 0.71 as the EC ratio increased from (0 to 100) %.

Redox reaction of Sn-polyacrylate electrodes in aprotic Na cell

Sn powder electrodes with polyacrylate binder are examined in aprotic Na cells. The Sn electrodes demonstrate electrochemical redox reaction to reversibly form Sn-Na intermetallic phases, such as Na15Sn4 in the voltage region between 0.0 and 0.7V vs. Na whereas Si, Ge, and Pb electrodes show less or no specific capacity in Na cells. The reversibility of the Sn electrodes is improved by polyacrylate as a binder and restriction of potential range between 0.0 and 0.8V. When fluoroethylene carbonate is added to propylene carbonate solution containing NaClO4, the Sn electrode performance with polyacrylate is further improved. The Sn electrode delivers ca. 500mAh g−1 for more than 20cycles, which is about two times larger reversible capacity compared with a hard-carbon negative electrode for Na-ion batteries.

Ternary Diagrams of Poly(vinylidene fluoride) and Poly[(vinylidene fluoride)‐co‐hexafluoropropene] in Propylene Carbonate and Dimethyl Sulfoxide

AbstractExperiments on the thermoreversible gelation of a ternary system composed of poly(vinylidene fluoride) (PVDF) and poly[(vinylidene fluoride)‐co‐hexafluoropropene] (P(VDF‐co‐HFP)) in propylene carbonate (PC) or DMSO solutions are carried out and the resulting ternary diagrams are plotted for various systems. The results show that the gelation occurs at relatively low concentrations. The miscibility area of the ternary diagram is larger with DMSO than with PC. In addition, the concentration at the gelation point increases with increasing temperature. The gelation line is almost independent of the molecular structure of PVDF in PC but varies in DMSO. This variation of the miscibility is essentially connected to the carboxylic functions on the PVDF chain.

Lithium electrochromism of atmospheric pressure plasma jet-synthesized NiO x C y thin films

Reversible lithium intercalation and deintercalation behavior of atmospheric pressure plasma jet (APPJ)-synthesized organonickel oxide (NiO x C y ) thin films under various substrate distances is testified in an electrolyte (1 M LiClO4–propylene carbonate solution) at low driving voltages from −0.5 to 1.5 V. Fast responses of 2 s bleaching at −0.5 V and 6 s coloration at +1.5 V are accomplished for the nano-porous NiO x C y thin films. This study reveals that a rapid synthesis of electrochromic NiO x C y thin films in a single process via APPJ by 21 s is investigated. This study presents a noteworthy electrochromic performance in a light modulation with up to 43% of transmittance variation and a coloration efficiency of 36.3 cm2/C at a wavelength of 830 nm after 200 cycles of cyclic voltammetry measurements.

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

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 (EMImBF(4)), 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 (Et(4)NBF(4)-PC 1M) was studied for comparison purposes. Carbon was produced from phenolic resin activated in CO(2). The porosity of the carbon samples were characterised by N(2) 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 EMImBF(4). The maximum energy density increased to 70 Wh kg(-1) (carbon) for RTIL EMImBF(4) from 35 Wh kg(-1)(carbon) for the organic electrolyte Et(4)NBF(4)-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 EMImBF(4) > DMPImTFSI > BMPyFAP > EMImN(CN)(2). The electrolyte and equivalent series resistance were in the order EMImN(CN)(2) < EMImBF(4) < DMPImTFSI < BMPyFAP.

Solvent Oligomerization during SEI Formation on Model Systems for Li-Ion Battery Anodes

We report the results of electrochemical quartz crystal microbalance (EQCM), and matrix assisted laser desorption ionization (MALDI) time of flight (TOF) mass spectrometry (MS) measurements along with detailed calculations examining the formation of the solid electrolyte interphase (SEI) on battery anode electrodes. EQCM analysis of Au and Sn surfaces in propylene carbonate (PC) and a 1:1 mixture of ethylene carbonate and dimethyl carbonate (EC:DMC) showed major irreversible mass uptake by the electrode surface especially during the first five cycles between +2 and 0.1 V vs. Li/Li+. MALDI-MS on emersed electrodes showed that long chain (m/z = 3000 on PC) oligomerized species were present on Au surfaces in PC and EC:DMC solvents, where oligomerized species formed in PC solutions showed higher mass ratios. The repeating units of the oligomer, visible as oscillations in the MALDI-MS, vary with the type of the solvent and electrode material. Sn surfaces initially showed formation of long chain polymers, but this material was not in evidence on electrode emersed after five cycles, which likely arises as a consequence of the catalytic involvement of Sn in decomposition of initially formed species. Density functional theory (DFT) calculations of cyclic solvent molecules suggested a radical initiated polymerization mechanism and predict oligomer subunits consistent with the experimental results.

Potential-induced phase transition of low-index Au single crystal surfaces in propylene carbonate solution

In situ scanning tunneling microscopy (STM) was employed to examine the surface structures of Au(111), Au(100), and Au(110) single crystals in propylene carbonate (PC) containing tetrabutylammonium perchlorate (TBAP). All three electrodes exhibited potential-induced phase transition between the reconstructed and unreconstructed (1 × 1) structures at negative and positive potentials, respectively. The potential-induced phase transition of the Au electrode surfaces is attributed to the interaction of the TBA cation and the perchlorate anion at the electrode surface, which is similar to that which takes place in aqueous solutions. In addition to static atomic structures, dynamic processes of both the reconstruction and the lifting of the reconstruction were investigated by means of in situ STM. The lifting of reconstructed Au(111)-(√3 × 22) on Au(111) to the (1 × 1) structure is completed within 1 min at a positive potential. The diffusion of Au atoms on the Au(100) plane in the PC solution proceeds more rapidly than that in the aqueous solution, suggesting that the PC solvent plays an important role in accelerating the diffusion of Au atoms.