Vapor Pressure Measurements Research Articles

Infrared Band Strengths and Other Properties of Three Interstellar Compounds—Amorphous Isocyanic Acid, Formaldehyde, and Formic Acid

Infrared (IR) spectral features of interstellar and solar system ices have been attributed to solid organic and inorganic compounds for over 50 yr, but in many cases the laboratory IR data needed to fully quantify such work have never been published, forcing researchers to rely on assumptions about gas- or liquid-phase measurements to interpret data for ices. Here, we report the first mid-IR intensity measurements for isocyanic acid (HNCO) ices that are free of such assumptions, providing new results for use by both observational and laboratory astrochemists. We also report similar new IR data for both formaldehyde (H2CO) and formic acid (HCOOH), which have been discussed in the astrochemical literature for decades, but again without adequate laboratory data to help quantify observational results. Densities and refractive indices of HNCO, H2CO, and HCOOH as amorphous ices also are reported. Two applications of the new H2CO work are presented, the first vapor-pressure measurements of solid H2CO, along with an enthalpy of sublimation, at 100 to 109 K and a set of IR intensities of H2CO in H2O + H2CO ices. Band strengths, absorption coefficients, and optical constants are calculated for all three compounds. Extensive comparisons are made to older results, which are not recommended for future use.

Physicochemical and Thermal Behaviors of Room-Temperature Phosphonium Ionic Liquids Based on Fluorosulfonyl(trifluoromethylsulfonyl)Amide Anion As Potential Electrolytes

Room-temperature ionic liquids (RTILs), i.e. organic molten salts with melting points below 100 ◦C, have been intensively developed for electrolytic media in various electrochemical systems due to the fact that RTILs have unique physicochemical properties such as favorable solubility of organic and inorganic compounds, relatively high ionic conductivity, no measurable vapor pressure, high thermal stability, low flammability, etc. Another advantage of RTILs is a purposive selection of the ion species and their designability. Although typical anion species employed for RTILs include sulfonylamide-based anions, e.g. bis(trifluoromethylsulfonyl)amide (N(SO2CF3)2 -, TFSA) and bis(fluorosulfonyl)amide (N(SO2F)2 -, FSA) anions, asymmetric fluorosulfonyl(trifluoromethylsulfonyl)amide (N(SO2F)(SO2CF3)-, FTA) anion have attracted attention in recent years. In our preliminary approach, FTA anion based RTILs in combination with quaternary phosphonium cationswe previously reported,1,2 examining their transport property behavior. In this work, we report design and synthesis of several FTA-based phosphonium RTILs (Fig. 1) as potential electrolytes available for electrochemical systems, summarizing their physicochemical and thermal characteristics including the thermal decomposition as well as the transport property behaviors.The preparation and purification of the phosphonium RTILs were carried out according to the procedures described in our previously published papers.1-3 The phosphonium RTILs were prepared by aqueous ion exchange reactions of the precursor phosphonium bromides with lithium FTA. The resulting crude RTILs was extracted by dichloromethane, and then purified by washing with pure water several times until no residual bromide anion was detected with the use of AgNO3. The RTILs was dried under high vacuum for at least 1 day at 80 ◦C prior to use. The physicochemical and electrochemical properties such as conductivity (ac impedance method, using a two-Pt electrode cell), viscosity (cone-plate type viscometer), density, melting point (DSC), thermal decomposition temperature (TGA) were measured under dry argon atmosphere.Several phosphonium RTILs melting at ambient temperatures were successfully prepared by combination with the FTA anion. Table 1 lists the physicochemical properties and thermal decomposition temperatures (10% weight loss) of the FTA-based phosphonium RTILs. All FTA-based phosphonium RTILs showed typical temperature-dependent behaviors for density, viscosity and electrical conductivity. It should be noted that P222(1O1)-FTA exhibited the lowest viscosity and the highest conductivity in the FTA-based phosphonium RTILs, which is attributed to the introducing effect of ether oxygen atom into the cation on the flexibility of the alkyl chain. On the other hand, the thermal decomposition temperatures of the FTA-based phosphonium RTILs tended to be relatively low (less than 300 ◦C) compared to those of TFSA-based RTILs. The detailed thermal decomposition behavior observed in the thermogravimetric traces will be discussed in comparison with both corresponding TFSA- and FSA-based RTILs.References1) K. Tsunashima, et al, Electrochem. Commun., 9, 2353 (2007).2) K. Tsunashima, et al, Electrochemistry, 75, 734 (2007).3) K. Tsunashima, et al, Electrochem. Commun., 13, 178 (2011). Figure 1

An Explorative Approach for Formulating Highly Performant, Scalable, Lithium Battery Separators

Introduction The lithium-ion technology has revolutionized the energy storage market and the demand for highly performant devices is rapidly expanding, also capable of satisfying hard/challenging operative conditions required in many technological sectors. For instance, large-scale applications (particularly, deep-water drilling devices, gas/oil industry, but also stationary power sources and automotive) require batteries able of safely operating even at high temperatures (around or above 100 °C), while maintaining acceptable performance and cycle life without significant degradation [1,2].However, commercial Li-ion batteries (LIBs) are temperature limited as they can only occasionally overcome 50-60 °C. The presence of volatile and flammable organic electrolyte solvents can lead to a dangerous chain of events such as overpressure, cell venting, burning and explosion, with rapid cell dismantling [3]. In addition, the LiPF6 salt (generally used in standard LIB electrolytes) is thermally unstable and, in the presence of even moisture and/or oxygen traces, is able of generating HF acid, thereby irreversibility ageing the electrochemical device and leading to cell performance decay [4-5]. In this scenario, an appealing approach for overcoming this drawback is the design of non-volatile, non-flammable, more thermally robust electrolyte formulations able of withstanding high temperatures [2].Ionic liquids, molten salts below 100 °C (often at room temperature or below), were proposed as advanced electrolyte solvents for improving the safety and reliability of LIB devices [6] due to their appealing peculiarities (i.e., no measurable vapor pressure, marked flame retardant properties, fast ion transport properties, high chemical/electrochemical/thermal stability, good power solvent) [7]. Phosphonium-based ionic liquids are expected to exhibit higher thermal and electrochemical stability compared to those containing ammonium cations [8-12]. Experimental In the present work, the attention has been focused on the tetrabutylphosphonium (P4444)+ cation, which has been selected because the steric hindrance and the symmetry of its structure are expected of allowing high thermal and electrochemical stability (with respect to the reduction process) [8-12], although these factors do not favor the ion transport properties and the low melting temperature. The (P4444)+ cation, commercially available as bromine salt (easily handled and purified), was coupled with selected anions of the per(fluoroalkylsulfonyl)imide family for their appealing thermal/electrochemical stability and good transport properties [9,13].The (P4444)+-based ionic liquids (PILs) were synthesized and purified according to an eco-friendly procedure, reported in detail elsewhere [7], which requires water as the only processing solvent. The quality control of the PIL materials was checked in terms of NMR, FT-IR, EDX and UV-Vis analysis where the physicochemical properties were studied through DSC and TGA techniques. The electrochemical characteristics were also examined in the presence of the LiTFSI salt (PIL:LiTFSI mole ratio = 4:1) in terms of ionic conductivity and electrochemical stability. Results The PIL materials were successfully synthesized with purity level overcoming 99.9 wt.%, i.e., in particular, the halide, moisture and lithium content was found below 5 ppm. The PIL electrolytes have exhibited very good thermal robustness (well above 250 °C) in conjunction with wide electrochemical stability window (close to 4.8 V vs the Li+/Li° redox couple). Fast ion transport properties (largely exceeding 10-3 S cm-1) were recorded at temperatures ranging from 80-120 °C. These results make the (P4444)+-based electrolytes rather appealing for high temperature lithium battery systems. The results are here presented and discussed.

New Applications of Knudsen Effusion Mass Spectrometry (KEMS) for Gas Evolution Analysis in Lithium-Ion Batteries

Kems4Bats, a new research group initiated under the BMBF's NanoMatFutur framework at Hochschule Mannheim, employs both established and innovative experimental methods to analyze thermal and gaseous emissions in lithium-ion batteries. Operating from a state-of-the-art laboratory equipped with advanced instrumentation, the group examines how variations in electrode materials and particle dimensions influence diffusion and gas generation. Key research focuses include studying diffusion processes, the formation of solid electrolyte interfaces, and the impacts of fast charging on battery aging. Significant achievements of Kems4Bats include the development of a new instrument based on the KEMS (Knudsen effusion mass spectrometry) method, which enables precise, real-time in-situ measurements of gas evolution in lithium-ion batteries. Moreover, this device allows for highly accurate measurements of vapor pressures, particularly for organic substances with high vapor pressures, such as electrolyte solvents. Additionally, the group has established a battery production line, enhancing the safety and effectiveness of these energy storage systems.The improvement and detailed study of lithium-ion batteries are essential for advancing energy storage technologies. Understanding how gases evolve within these batteries during their formation, operational cycles, and aging is crucial for enhancing their performance and safety. Historically, Knudsen Effusion Mass Spectrometry (KEMS) has been an effective method for measuring the temperature-dependent vapor pressures of various materials, both organic and inorganic. This technique aids in calculating important thermodynamic properties. This study expands the application of KEMS to investigate gas evolution in lithium-ion batteries, marking a significant development in battery diagnostics.A unique prototype was developed to modify the KEMS approach, allowing for accurate monitoring of gas species evolution in lithium-ion batteries. This innovation not only provides detailed insights into the types and quantities of gases produced at different stages of the battery lifecycle but also broadens the traditional boundaries of KEMS measurements. Our modified system allows for the analysis of substances with high vapor pressures, such as electrolyte components, which were previously challenging to study due to methodological limitations.The results of this research shows the complex patterns of gas formation in lithium-ion batteries, providing essential insights for improving battery design and establishing higher safety standards. This research not only advances the field of battery technology but also highlights the adaptability of KEMS as a powerful tool in materials science.

Impact of Temperature on the Diffusion in Silicon-Based Anodes

Kems4Bats, established within the BMBF framework NanoMatFutur at Hochschule Mannheim, focuses on understanding heat and gas evolution in Li-ion batteries through advanced experimental methods. The group integrates thermodynamic data and new insights into phenomena like diffusion, solid electrolyte interface formation, aging from high-power charging, and thermal runaway. A state-of-the-art laboratory with cutting-edge equipment allows detailed study of materials properties affecting diffusion coefficients and heat and gas evolution, such as electrode composition and particle size. Key achievements include setting up a battery production line and developing a novel device, KEMS (Knudsen-Effusion Mass-Spectrometry), for vapor pressure measurements, enhancing battery safety and performance.Building on the experimental capabilities and insights gained by the Kems4Bats group, our research also zeroes in on specific materials that hold promise for enhancing battery performance. Among these, silicon stands out due to its high theoretical capacity, making it an ideal candidate for the next generation of anode materials in lithium-ion batteries. However, despite its potential, certain thermodynamic properties of silicon remain inadequately explored, notably diffusion. Diffusion is crucial as it facilitates the transport of ions to the active material's surface, essential for lithiation. This process is influenced by various factors including the state of charge (SOC) and cell temperature.This study explores the impact of temperature on the diffusion coefficient of self-made silicon anodes, composed of nanoparticles mixed with carbon black. The weight ratio between the anode components is 45/45/10 (Si/CB/CMC). PAT-Cells are used to assemble half-cells with a lithium-counter electrode. The half-cells, organized into four groups of at least three cells each, are examined at different temperatures (15°C, 25°C, 40°C, and 60°C) post-formation. The diffusion coefficient is determined via the galvanostatic incremental titration technique (GITT). Furthermore, incremental capacity analysis (ICA) is conducted to determine the impact of phase changes in the active material on the coefficient and to show the impact of temperature on the anodes' capacity.In summary, our investigation provides crucial insights into the temperature-dependent behavior of the diffusion coefficient in silicon anodes, a key component for enhancing lithium-ion battery performance. By analyzing the effects of temperature on both the diffusion process and phase changes within silicon-carbon black composite anodes, this study underscores the significant influence of thermal conditions on the efficiency and capacity of next-generation battery technologies. These findings not only contribute to a deeper understanding of silicon anodes' operational dynamics but also highlight the critical role of temperature management in optimizing lithium-ion battery performance.

Physicochemical study of the processes of b-cyclodextrin hydrates dehydration

The research involved synthesizing b-cyclodextrin hydrates of the b-CD·nH2O (n = 11.9–0.9) composition. The obtained compounds were studied by powder X-ray diffraction (XRD), which revealed the transition from a monoclinic unit cell to an orthorhombic one with a decrease in the water content in the samples. The pressure of saturated vapor of the water in the b-CD·nH2O (n = 10.6–7.0) hydrates was measured by static tensimetry with membrane null-manometer over a wide temperature range (293–384 K) under conditions of a quasi-constant hydrate composition. The measured vapor pressure increases in proportion to the increase in the water content of the hydrate samples. The experimental data reduced to a single composition of b-CD·1H2O were approximated by the lnp(1/T) equation, from which the thermodynamic parameters (∆prH°T and ∆prS°T) of the process of b-cyclodextrin hydrate dehydration were calculated. This information was used to estimate the binding energies of the water molecules to the b-CD framework

Equation of state for nanopores and shale: Pore size–dependent acentric factor

Nanopores pose a challenge to phase-behavior modeling when using the equation of state (EOS), and common methods do not capture their vapor pressure or become difficult to implement because they require additional tuning parameters. This study focuses on improving the vapor-pressure prediction of EOS in nanopores by proposing a pore size–dependent acentric factor (ACF). It determines the ACF from experimental data and implements it in EOS along with critical pressure and temperature. The proposed approach is then applied to the vapor-pressure measurements of nitrogen, argon, oxygen, methane, and ethane in pores ranging from 3.5 nm to 8.1 nm. The results show that the ACF in nanopores increases as the pore size decreases, and the degree of size dependency varies across different pure components. The results also demonstrate that the proposed approach enables EOS predictions to match the measurements with good accuracy. This study quantifies the effects of pore size on the ACF for the first time and presents simple correlations for estimating the ACF when the pore radius is smaller than 10 nm. The proposed approach simplifies the application of EOS in nanopores and unconventional hydrocarbon reservoirs.

A novel instrument for the accurate and direct measurement of saturation vapor pressures of low-volatile substances

Aerosols often act as the seed around which clouds form, yet much remains to be learned about how they grow in the atmosphere. Henrik Pedersen and Aurelien Dantan tell us about their work in developing new instruments for measuring saturation vapour pressure and its wider relevance to understanding the influence of aerosols on the climate system.

Thermodynamic studies in the Ce-Te binary system

Vapour pressure measurements in the Ce-Te system were carried out employing the isopiestic method. Four sets of isopiestic experimental runs were performed for the temperature range 805 – 1035 K for the composition span from ∼65 to ∼75 at% Te covering the Ce-Te phase diagram region encompassing the intermetallic compounds CeTe2, Ce2Te5 and CeTe3. Activity measurements, partial enthalpy of mixing of tellurium for CeTe2 intermetallic compound and Gibbs energy of the reaction between CeTe2 and Ce2Te5 are reported. A few phase boundaries of the Ce-Te phase diagram were redefined with the measured data and reported.

An activity coefficient model for mixed-solvent electrolyte mixtures based on Gibbs–Duhem’s equation: A case study of mixtures of water, KCl and ethanol

Thermodynamic properties of mixtures with several fluid components and electrolytes are challenging to model. Models are needed to develop and improve a wide range of electrochemical systems such as fuel cells, lithium-ion batteries, and processes with ion-exchange membranes. In the literature, activity coefficients are extracted using fundamentally different experimental methods that rely on electrochemical cells, vapour pressure measurements, solubility measurements, etc. The reference states of the activity coefficients obtained from these methods are likely to differ. This makes it difficult to combine or compare activity coefficient models from different sources. In this work, we present a method using Gibbs–Duhem’s equation for the development of activity coefficient models of mixtures that are based on experimental data from different methods. We use the ternary mixture of KCl, H2O and ethanol as example. First, empirical expressions are developed for the logarithm of the activity coefficients of KCl and ethanol. The expression for the activity coefficient of H2O is next derived using Gibbs–Duhem’s equation. The resulting three activity coefficient models are fitted to available experimentally data from several sources, generating linear and relatively low-complexity activity coefficient models. The empirical activity coefficient models are next compared to the electrolyte cubic plus association (e-CPA) equation of state. The models give saturation pressures in ternary mixtures that have average absolute relative deviations for water/ethanol of 8.3/3.4% for the empirical model and 11.8/3.3% for e-CPA. Experimental data reduction procedures for concentration cells, formation cells, and vapour pressure measurements are discussed, and the freedom to choose the reference state and the consequences are highlighted.

Phase transition study of bathophenanthroline and bathocuproine: A multitechnique approach

The thermal behaviour of bathophenanthroline and bathocuproine has been studied using several techniques, namely, differential scanning calorimetry and thermogravimetry. To determine their respective enthalpies of sublimation, vapor pressure measurements were carried out using different methods, such as Knudsen effusion mass loss/mass spectrometry, isothermal thermogravimetry, and a quartz crystal microbalance technique. Furthermore, the enthalpies of sublimation were determined by measuring the heat change of the sublimation process using high-temperature Calvet microcalorimetry.The results obtained in this work allowed the determination of the standard molar enthalpies of sublimation at 298.15 K, for bathophenanthroline and bathocuproine. The values obtained were (183.8 ± 2.2) kJ⋅mol−1 and (206.2 ± 2.8) kJ⋅mol−1, respectively. Additionally, the standard molar enthalpies of fusion were determined to be (30.4 ± 0.4) kJ⋅mol−1 and (26.5 ± 1.6) kJ⋅mol−1 for bathophenanthroline and bathocuproine, respectively. The analysis of the results allows a deeper understanding of the phase transition behavior for these compounds from the condensed to the gaseous phases, elucidating molecular decomposition and the inherent intermolecular forces governing the species.

Exploring the boiling point elevation of multicomponent salt solution by changing vapor pressure and solution composition

This paper applies thermodynamics theory to analyze the main factors that affect the boiling point elevation (BPE) of salt solutions. By using the vapor pressure measurement method, boiling point experiments were conducted on several common inorganic salts used in industrial wastewater treatment and desalination at different concentrations and temperatures. The experimental data shows that the BPE of a salt solution is approximately a quadratic function of the solution temperature at constant concentration, and the BPE of tri-ion salt solutions tends to be higher than that of NaCl solution at the same concentration. Based on theoretical analysis and a summary of experimental results, it was found that BPE is not only related to solute concentration but also to the number of ionized solute ions. It was also found that replacing the compound concentration with the ion concentration as the independent variable of concentration can reduce the impact of electrolyte ionization and reduce variable parameters. Furthermore, the impact of ion types on BPE was studied in mixed salt solutions. The results show that the higher the average ion activity coefficient of the solute, the higher the boiling point of the solution. Through nonlinear fitting analysis of experimental data, a correlation for calculating the BPE of multi-component salt solutions in industrial water treatment is proposed based on solution temperature and ion concentration.

A new setup for measurements of absolute saturation vapor pressures using a dynamical method: Experimental concept and validation.

We describe a new experimental system for direct measurements of the absolute saturation vapor pressures of liquid or solid samples. The setup allows the isolation of the sample under steady conditions in an ultra-high vacuum chamber, where the measurement of the sample's vapor pressure as a function of its temperature can be performed in a range around room temperature and in a pressure range defined only by the applied absolute pressure sensor. We characterize the setup and illustrate its capability to measure saturation vapor pressures as well as enthalpies of evaporation around room temperature with explicit measurements on four liquid compounds (diethyl phthalate, 1-decanol, 1-heptanol, and 1-hexanol) for which accurate vapor pressures have previously been reported.

Design of a Simple Isoteniscope for Use in a Student Laboratory for Measurements of Vapor Pressure of Liquids

Design of a Simple Isoteniscope for Use in a Student Laboratory for Measurements of Vapor Pressure of Liquids

New static apparatus STAT9 for vapor pressure measurements at temperatures up to 463 K

In this work, a state-of-the-art static apparatus for vapor pressure measurements in a temperature range of 363−463 K and a wide pressure range of 1−13,330 Pa is introduced and described. The performance of the apparatus was evaluated by a meticulous procedure of measuring the vapor pressure of five reference materials of different volatility, anthracene, benzophenone, ferrocene, naphthalene, and dibenzothiophene. The last two compounds were studied in the blind test regime, i.e., the results were compared to literature only after finishing the experiments. During benchmarking the performance of the apparatus, it was found appropriate to develop new vapor pressure equations for ferrocene and anthracene that included high-temperature data from the STAT9 apparatus. By combining the new data with previously selected vapor pressures, sublimation enthalpies, and ideal-gas and condensed phase heat capacities, we have obtained a consistent sublimation pressure equation for anthracene and ferrocene. For anthracene, the correlation procedure covered melting properties and liquid-phase vapor pressure data to support the description of the high-temperature region. The revised vapor pressure equations and sublimation enthalpies may serve as solid foundation for future research in this field.

Connection between partial pressure, volatility, and the Soret effect elucidated using simulations of nonideal supercritical fluid mixtures.

Building on recent simulation work, it is demonstrated using molecular dynamics simulations of two-component fluid mixtures that the chemical contribution to the Soret effect in two-component nonideal fluid mixtures arises due to differences in how the partial pressures of the components respond to temperature and density gradients. Further insight is obtained by reviewing the connection between activity and deviations from Raoult's law in the measurement of the vapor pressure of a liquid mixture. A new parameter γsS, defined in a manner similar to the activity coefficient, is used to characterize differences deviations from "ideal" behavior. It is then shown that the difference γ2S-γ1S is predictive of the signof the Soret coefficient and is correlated to its magnitude. We hence connect the Soret effect to the relative volatility of the components of a fluid mixture, with the more volatile component enriched in the low-density, high-temperature region, and the less volatile component enriched in the high-density, low-temperature region. Because γsS is closely connected to the activity coefficient, this suggests the possibility that measurement of partial vapor pressures might be used to indirectly determine the Soret coefficient. It is proposed that the insight obtained here is quite general and should be applicable to a wide range of materials systems. An attempt is made to understand how these results might apply to other materials systems including interstitials in solids and multicomponent solids with interdiffusion occurring via a vacancy mechanism.

Saturated vapor pressure measurement and fitting analysis of green insulating gas C4F7N within the temperature range of 251 to 309 K

Saturated vapor pressure measurement and fitting analysis of green insulating gas C₄F₇N within the temperature range of 251 to 309 K

Vapour pressure measurements on Nd–Te system

Vapour pressure measurements on Nd–Te system

Modeling Henry's law and phase separations of water-NaCl-organic mixtures with solvation and ion-pairing.

Empirical measurements of solution vapor pressure of ternary acetonitrile (MeCN) H2O-NaCl-MeCN mixtures were recorded, with NaCl concentrations ranging from zero to the saturation limit, and MeCN concentrations ranging from zero to an absolute mole fraction of 0.64. After accounting for speciation, the variability of the Henry's law coefficient at vapor-liquid equilibrium (VLE) of MeCN ternary mixtures decreased from 107% to 5.1%. Solute speciation was modeled using a mass action solution model that incorporates solute solvation and ion-pairing phenomena. Two empirically determined equilibrium constants corresponding to solute dissociation and ion pairing were utilized for each solute. When speciation effects were considered, the solid-liquid equilibrium of H2O-NaCl-MeCN mixtures appear to be governed by a simple saturation equilibrium constant that is consistent with the binary H2O-NaCl saturation coefficient. Further, our results indicate that the precipitation of NaCl in the MeCN ternary mixtures was not governed by changes in the dielectric constant. Our model indicates that the compositions of the salt-induced liquid-liquid equilibrium (LLE) boundary of the H2O-NaCl-MeCN mixture correspond to the binary plateau activity of MeCN, a range of concentrations over which the activity remains largely invariant in the binary water-MeCN system. Broader comparisons with other ternary miscible organic solvent (MOS) mixtures suggest that salt-induced liquid-liquid equilibrium exists if: (1) the solution displays a positive deviation from the ideal limits governed by Raoult's law; and (2) the minimum of the mixing free energy profile for the binary water-MOS system is organic-rich. This work is one of the first applications of speciation-based solution models to a ternary system, and the first that includes an organic solute.

Comparative Study on Transport Property of Asymmetric Fluorosulfonyl(trifluoromethylsulfonyl)Amide-Based Phosphonium Ionic Liquids

Room-temperature ionic liquids (RTILs), i.e. organic molten salts with melting points below ambient temperature, have been regarded as potential electrolytes for various electrochemical systems, because RTILs have unique physicochemical properties such as favorable solubility of organic and inorganic compounds, relatively high ionic conductivity, no measurable vapor pressure, high thermal stability, low flammability, etc. The quaternary phosphonium cation based RTILs have attracted attention in recent years due to their high chemical and thermal stabilities. We have proposed and synthesized a class of low viscous and highly conductive RTILs based on triethylalkylphosphonium cations in combination with typical sulfonylamide-based anions, e.g. bis(trifluoromethylsulfonyl)amide (N(SO2CF3)2 -, TFSA) and bis(fluorosulfonyl)amide (N(SO2F)2 -, FSA) anions.1,2 Our recent approaches include a design and synthesis of low-melting phosphonium based RTILs together with asymmetric fluorosulfonyl(trifluoromethylsulfonyl)amide (N(SO2F)(SO2CF3)-, FTA) anion. In this work, we report the transport property and unique viscosity behavior of several FTA anion based phosphonium RTILs as shown Fig. 1. The FTA-based phosphonium RTILs was synthesized by aqueous ion exchange reaction of the precursor quaternary phosphonium halides with lithium FTA. The crude RTILs obtained were hydrophobic and purified by washing with pure water several times in order to remove residual metal and halide ions. The RTILs thus prepared were dried under high vacuum for at least 1 day. The physicochemical properties of RTILs, e.g. density, viscosity, conductivity (ac impedance method), were measured at elevated temperatures under argon atmosphere.Several low-melting phosphonium RTILs were successfully prepared by combination with FTA anion (P2225, P2228 and P4441-FTA). All FTA-based phosphonium RTILs showed typical temperature dependent behaviors for density, viscosity and electrical conductivity. The conductivities of FTA-based phosphonium RTILs were higher and lower than those of corresponding TFSA- and FSA-based phosphonium RTILs, respectively; however, it should be noted that the viscosities of FTA-based phosphonium RTILs were the lowest in the phosphonium RTILs as depicted in Fig. 2. To our knowledge, such a unique viscosity behavior has not been previously reported in the FTA-based ammonium based RTILs. The detailed transport property and electrolytic behaviors such as the Arrhenius plots of viscosity and conductivity with VTF fitting and the Walden plots will be also discussed in comparison with both corresponding TFSA- and FSA-based RTILs.References1) K. Tsunashima, et al, Electrochem. Commun., 9, 2353 (2007).2) K. Tsunashima, et al, Electrochem. Commun., 13, 178 (2011). Figure 1