Phosphonium-based Ionic Liquids Research Articles

Physicochemical and Thermodynamic Investigation of Ethanolic Solution of Phosphonium-Based Ionic Liquids─Measurements, Correlations, and Application to Absorption Cycles

Physicochemical and Thermodynamic Investigation of Ethanolic Solution of Phosphonium-Based Ionic Liquids─Measurements, Correlations, and Application to Absorption Cycles

Effect of the anion in phosphonium-based ionic liquids to recovery efficiently 2-propanol from an azeotropic mixture with water

Effect of the anion in phosphonium-based ionic liquids to recovery efficiently 2-propanol from an azeotropic mixture with water

Effect of phosphonium‐based ionic liquids on the structuration and physical properties of LIonomers

AbstractIn this study, LIonomers families based on phosphonium ILs have been successfully developed. These LIonomers are designed from the combination of various phosphonium‐based ionic liquids (PhILs) with different counter anions including tetradecyl (trihexyl) phosphonium bis (2,4,4‐trimethylpentyl) phosphinate (P+TMP), tributyl (ethyl) phosphonium diethyl phosphate (P+DEP), trihexyl (tetradecyl) phosphonium chloride (P+Cl) and trihexyl (tetradecyl) phosphonium acetate (P+Ac). Here, the interactions between maleic anhydride groups (MA) of the maleic anhydride‐grafted polypropylene (PPgMA) and PhILs within LIonomers have been investigated by NMR, whose intensity depends on the chemical nature of cation/anion pairs. Then, viscosity in the molten state was considered as a probe of the interaction intensity between polar groups of grafted polypropylenes and the phosphonium cation. The proper one can be tuned from the nature (P+TMP vs. P+Ac vs. P+Cl), from the steric hindrance, that is, relevant to the conformation of PhILs (P+DEP vs. P+TMP / P+Ac / P+Cl), and by MA content, as well as the extent of generated ionic chains from polar groups of matrices as “head” and associated anion/cation pairs. The effect of these generated ionic interactions on crystallization process and mechanical properties had been also investigated by DSC in non‐isothermal conditions, and tensile tests. Depending of the steric hindrance of the phosphonium ILs playing a key role on the interactions with PPgMA chains, an increase of the ductility versus a plasticizing effect can be obtained as function of the targeted applications.

Preparation and Physicochemical Characterization of Phosphonium-Based Ionic Liquids Containing Carboxylate Anions

Ionic liquids (ILs) are organic salts composed of cation and anion with melting points below 100°C. They have unique characteristic features.1) ILs are also promising liquid materials available for various applications because their function can be easily controlled by changing the combination of cations and anions and by introducing substituents. Among the numerous ILs, considerable ILs based on carboxylate anions have been reported. On the other hand, several published papers reported ILs based on quaternary phosphonium cations, demonstrating relatively high transport properties and thermal stability2). We report here the preparation and physicochemical properties of ILs based on triethyloctylphosphonium (P2228) and tributyloctylphosphonium (P4448) cations together with various carboxylate anions.The intermediate hydroxides were obtained by adding an anion exchange resin (Amberlite IRN78 OH) into the precursor bromide aqueous solutions. Equimolar amounts of carboxylic acids (formic, acetic, propionic, butyric and octanoic acids) were added to the hydroxide solutions to form carboxylate-based phosphonium salts. The salts obtained were isolated by evaporation and then were dried under high vacuum at 50 °C. The physicochemical properties of ILs, e.g. density, viscosity, conductivity and thermal decomposition temperature were measured.Table 1 shows the physicochemical properties of the ILs at 25 °C. P2228-PrCO2 became a solid at room temperature, while P2228-HCO2, P2228-MeCO2, and P2228-EtCO2 became viscous liquids at room temperature. Furthermore, all P4448-based salts became viscous liquids at room temperature. The density of each IL was increased with decreasing the carbon numbers of the alkyl chains in carboxylate anions. The number density also showed similar tendency to the density. These results indicate that the number density of the formate was the highest since the anion size was the smallest. The viscosity of each ILs was decreased with increasing the carbon numbers of the alkyl chains in carboxylate anions. Although the details of the relationship between measured viscosity and the carbon numbers of the alkyl chains in carboxylate anions still remain unclear at present, it is thought to be the charge distribution of the anions is one of the factors. The acetate-, propionate-, butyrate-, and octanoate-based ILs showed high thermal decomposition temperatures around 270 to 300°C. However, the formate-based ionic liquid showed lower thermal stability, which might be due to the decarboxylation of the formate anion. Figure 1

Molecular simulation of CO2 capturing by dual functionalized phosphonium-based amino acid ionic liquids

Various solvents have been proposed considering the importance of CO2 gas removal from the environment. Over the past few decades, ionic liquids (ILs) have elicited much attention due to their unique properties. In this regard, capturing the CO2 gas by phosphonium-based amino acid ILs (AAILs) was studied by molecular dynamics (MD) simulation. The effect of cation functionalization was studied. The anion was glycinate, [GLY]-, and the cation was tetrabutylphosphonium, [P4444]+, functionalized by different functional groups including acidic (−COOH), alcoholic (−OH), amine (−ΝΗ2), and ether (−OCH3). Density, absorption energy, radial distribution function (RDF), mean square displacement (MSD), concentration profile, free volume, and fractional free volume were under investigation. According to density values calculated from MD simulation, functionalized AAIL with a carboxylic acid group ([P4444COOH][Gly]) is the most concentrated system with the maximum interaction energy between AAIL and the trapped CO2 gas equal to − 1.917 kcal.mol−1. In addition, the lowest volume variation was observed through this physical absorption. RDF analysis reveals that anion interaction with CO2 gas is the most considerable one in the case of [P4444COOH][Gly] AAIL. The CO2 uptake is 2:1 for functionalized AAILs that shows cation functionalization improves CO2 gas absorption capacity; each mole of [P4444COOH][Gly] AAIL is capable of surrounding 2.11 mol of CO2. Finally, the gas diffusion coefficient is the lowest one in [P4444COOH][Gly] AAIL as the solvent-free volume is observed as a continuous channel to trap CO2 gas with the lowest gas diffusivity parameter.

Selective extraction of Ti(IV) from acidic sulfate media by phosphonium-based ionic liquids and stripping with sulfuric acid

The Ti(IV) liquid-liquid extraction from acidic sulfate media has been investigated by the ionic liquids trihexyl(tetradecyl)phosphonium chloride [P66614+][Cl−] and trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate [P66614+][BTMPP−], diluted in 5% (v/v) 1-decanol/kerosene. The Room Temperature Ionic Liquids (RTIL) showed fast extraction kinetics reaching equilibration after 2 min, requiring a 450 rpm stirring rate. For [P66614+][Cl−] at 0.01 mol L−1, the maximum extraction efficiency was 30% from H2SO4 solution of 11 mol L−1. The IL [P66614+][BTMPP−] shows better Ti(IV) extraction than [P66614+][Cl−], and two maximum extraction conditions were observed at 0.1 and 7.3 mol L−1 H2SO4 due to the dual mechanism; both cationic and anionic exchange reactions, reaching 60% and 49% extraction efficiency, respectively.The increase in [P66614+][BTMPP−] concentration to 0.06 mol L−1, increases the extraction yield to 95.9%. The Fourier transform infrared FTIR characterization confirmed the presence of Ti(IV) in the organic phases, and the modification in the phosphonium bonds was correlated to the role of the ionic liquids in the Ti(IV) extraction. The organic phase containing 0.02 mol L−1 [P66614+][BTMPP−] can be loaded with 0.197 g/L of Ti(IV) from 7.3 mol L−1 H2SO4 media. In contrast, at 0.1 mol L−1 H2SO4, an increase in the Ti(IV) concentration promotes the polymerization in the form Ti-O-Ti-O-Ti inhibiting the extraction efficiency. The H2SO4 solution at 2 mol L−1 was the best stripping agent to achieve a high Ti(IV) recovery of 97%. The organic phase was reused for four cycles, and the extraction and stripping efficiencies remained unchanged after the third cycle. The selective separation of Ti(IV) from a mixture containing Fe(III) was reached with a separation factor of 78.4, with a 2.51% Fe(III) extraction and containing only 0.25 mg L−1 of Fe(III) in the stripping phase. The proposed system avoids the main problems associated with Ti(IV) recovery from acidic sulfate media.

Effect of surface wetting on tribological behavior for laser textured steel using ionic liquid-based lubricants

In this study, the effect of surface wettability on the tribological performance is evaluated through a ball-on-flat reciprocating wear test. The substrate material, M2 tool steel, is laser processed and then functionalized with fluorocarbon and nitrile chemistry to achieve distinct oleophobicity and oleophilicity, respectively, but with a similar nanoscale surface texture. The poly-alpha-olefin (PAO) base oil is used as the baseline lubricant, and ammonium- and phosphonium-based oil-miscible ionic liquids (ILs) are used as additives. The interaction between the nanoscale textured steel surface and ionic liquid-based oils is investigated. A set of reciprocating wear tests are performed to identify the wear and frictional mechanisms of the tribosystem consisting of the surface-engineered, flat M2 tool steel specimen and a standard, surface-polished steel ball. Results show that the oleophobic flat surface results in a lower friction, while the oleophilic surface modification leads to a better wear protection to the flat surface. Ammonium-based IL provides the highest friction reduction, while the phosphonium-based IL provide an improved wear protection. Click here and insert your abstract text.© 2023 Society of Manufacturing Engineers (SME). Published by Elsevier Ltd. All rights reserved.This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/)Peer-review under responsibility of the Scientific Committee of the NAMRI/SME.

Change of Conduction Mechanism in Polymer/Single Wall Carbon Nanotube Composites upon Introduction of Ionic Liquids and Their Investigation by Transient Absorption Spectroscopy: Implication for Thermoelectric Applications.

Polymer composites based on polycarbonate (PC) and polyether ether ketone (PEEK) filled with single-walled carbon nanotubes (SWCNTs, 0.5-2.0 wt %) were melt-mixed to investigate their suitability for thermoelectric applications. Both types of polymer composites exhibited positive Seebeck coefficients (S), indicative for p-type thermoelectric materials. As an additive to improve the thermoelectric performance, three different ionic liquids (ILs), specifically THTDPCl, BMIMPF6, and OMIMCl, were added with the aim to change the thermoelectric conduction type of the composites from p-type to n-type. It was found that in both composite types, among the three ILs employed, only the phosphonium-based IL THTDPCl was able to activate the p- to n-type switching. Moreover, it is revealed that for the thermoelectric parameters and performance, the SWCNT:lL ratio plays a role. In the selected systems, S-values between 61.3 μV/K (PEEK/0.75 wt % SWCNT) and -37.1 μV/K (PEEK/0.75 wt % SWCNT + 3 wt % THTDPCl) were reached. In order to shed light on the physical origins of the thermoelectric properties, the PC-based composites were studied using ultrafast laser time-resolved transient absorption spectroscopy (TAS). The TAS studies revealed that the introduction of ILs in the developed PC/CNT composites leads to the formation of biexcitons when compared to the IL-free composites. Moreover, no direct correlation between S and exciton lifetimes was found for the IL-containing composites. Instead, the exciton lifetime decreases while the conductivity seems to increase due to the availability of more free-charge carriers in the polymer matrix.

Tailored pretreatment of serum samples and biomarker extraction afforded by ionic liquids as constituents of aqueous biphasic systems

Prostate cancer serum biomarkers, such as the U.S. Food and Drug Administration (FDA)-approved prostate specific antigen (PSA), are valuable markers of diagnosis, response to treatment and disease progression. Despite the expected benefits of using PSA to better manage the mortality and morbidity associated to prostate cancer, sample complexity and interference within analysis make its quantification in serum a high-cost and strenuous assignment. Here, we make use of the simple preparation, water-rich environment, and selectivity of aqueous biphasic systems (ABS) to develop alternative serum pretreatment strategies. A set of ammonium- and phosphonium-based ionic liquids (ILs) were used as either main phase-forming agents in IL-salt ABS or as adjuvants in polymer-salt ABS, allowing to explore the IL designer solvent nature and versatile role in ABS formation and performance. Serum pretreatment efficiency was evaluated by the capacity of each ABS to simultaneously deplete high abundance serum proteins (immunoglobulin G, IgG, and human serum albumin, HSA) at the systems’ interphase (thus, generating a three-phase partitioning system – ABS-TPP) and extract PSA to a single ABS phase. Regardless of the ABS typology under appraisal (IL-salt or polymer-salt-IL), the proper design of the IL structure is critical for both the ability to deplete high abundance serum proteins and extract PSA. The results demonstrate that, in addition to the proper choice of the ABS typology, a careful adjustment of the IL hydrophobicity is key to achieve the simultaneous depletion of high-abundance proteins and complete PSA extraction in a single step, creating new approaches for PSA analysis and its application in diagnosis/prognosis.

Wetting behaviour of phosphonium-based halogen-free ionic liquids as lubricant additives on various metal surfaces

Metalworking fluids (MWFs) have high demand in manufacturing industries as they reduce the friction and wear of the surfaces in contact and improve the life of the system. Traditionally, petroleum-based MWFs are used, which may cause major health risks to machine operators and have a detrimental effect on the environment. Ionic liquids (ILs) have commenced as a potential alternative to conventional MWFs due to their unique properties such as low or negligible volatility, high polarity, high thermal stability, and better spreadability. However, the majority of the investigated ILs contain halogen-based anions, which are moisture sensitive and have the potential to generate hazardous halogen acids. These acids are harmful to the environment and have the potential to corrode working surfaces. The ILs properties such as viscosity, and wettability play an important role in the tribological performance of sliding pairs. This research work examines the wetting behaviour of one phosphonium-based halogen-free ILs and two halogen-based ILs as an additive to canola oil on mild steel, stainless steel, aluminum and titanium alloys. For comparison, the wetting behaviour of pure canola oil on different alloys was also examined using a contact angle goniometer. The finding suggests that wetting behaviour of phosphonium-based halogen-free ILs blended with canola oil shows a low contact angle for all different alloys due to the presence of long alkyl chain as compared to other MWFs. Furthermore, the wetting behaviour of the same MWFs varies for different metal surfaces due to the intermolecular interaction between ions of ILs and the surface adsorption properties of different metals. Presumably, this study shows the potential of wetting behaviour/spreadability of phosphonium-based halogen-free ILs as lubricant additives on various metal surfaces. The phosphonium-based halogen-free ILs blended with canola oil shows contact angle in the range of 23° to 28° at the stabilizing time of 1000 ms on the surface polished with 320G abrasive sheet for all materials, whereas, with canola oil, the contact angle varies in between 28° to 38° the with same parametric conditions. Overall, 27% and 22% improvements in spreadability were observed using phosphonium-based halogen-free ILs blended in canola oil on the surface of mild steel and titanium, respectively for polished surfaces with 320G abrasive sheet after stabilizing time of 1000 ms. At the same parameters, for steel and aluminum, only 7% and 8% improvements in spreadability were observed, respectively.

Phosphonium-based ionic liquids as grease additives in rolling bearing tests

Two phosphonium-derived ionic liquids: trihexyltetradecylphosphonium bis(2-ethylhexyl)phosphate (IL1) and trihexyltetradecylphosphonium tricyanomethanide (IL2) were used as additives in lithium complex- (G1) and anhydrous calcium-based (G2) greases at 5 wt%. Friction torque and wear tests were performed using a modified four-ball machine for testing rolling bearings in order to determine the friction and wear reducing properties of these grease samples in a real component. The IL2 improved the friction reduction performance of both greases, especially G1. Both ILs improved the antiwear behaviour of grease G2. Grease G2 showed higher oxidation and thermal ageing levels than G1, but the addition of the ILs, IL2 in particular, improved this issue.

The surface chemistry of ionic liquid-treated CsPbBr3 quantum dots.

The power conversion efficiencies of lead halide perovskite thin film solar cells have surged in the short time since their inception. Compounds, such as ionic liquids (ILs), have been explored as chemical additives and interface modifiers in perovskite solar cells, contributing to the rapid increase in cell efficiencies. However, due to the small surface area-to-volume ratio of the large grained polycrystalline halide perovskite films, an atomistic understanding of the interaction between ILs and perovskite surfaces is limited. Here, we use quantum dots (QDs) to study the coordinative surface interaction between phosphonium-based ILs and CsPbBr3. When native oleylammonium oleate ligands are exchanged off the QD surface with the phosphonium cation as well as the IL anion, a threefold increase in photoluminescent quantum yield of as-synthesized QDs is observed. The CsPbBr3 QD structure, shape, and size remain unchanged after ligand exchange, indicating only a surface ligand interaction at approximately equimolar additions of the IL. Increased concentrations of the IL lead to a disadvantageous phase change and a concomitant decrease in photoluminescent quantum yields. Valuable information regarding the coordinative interaction between certain ILs and lead halide perovskites has been elucidated and can be used for informed pairing of beneficial combinations of IL cations and anions.

Solubility and Stability of Carotenoids in Ammonium- and Phosphonium-Based Ionic Liquids: Effect of Solvent Nature, Temperature and Water.

Ionic liquids (ILs) have arisen as alternatives to organic solvents and been used in natural pigment extraction in recent decades. However, the solubility and stability of carotenoids in phosphonium- and ammonium-based ILs are insufficiently explored. In this work, the physicochemical properties of the ILs, and the dissolution behavior and storage stability of three carotenoids (astaxanthin, β-carotene, and lutein) in the IL aqueous solution were investigated. The results showed that the solubility of the carotenoids in the acidic IL solution is higher than that in the alkaline IL solution, and the optimal pH is about 6. The solubility of astaxanthin (40 mg/100 g), β-carotene (105 mg/100 g), and lutein (5250 mg/100 g) was the highest in tributyloctylphosphonium chloride ([P4448]Cl) due to the van der Waals forces with [P4448]+ and hydrogen bonding with Cl-. A high temperature was beneficial to improve the solubility, but it can reduce the storage stability. Water has no significant effect on the carotenoid stability, but a high water content decreases the carotenoid solubility. A IL water content of 10-20%, an extraction temperature of 338.15 K, and a storage temperature of less than 298.15 K are beneficial for reducing the IL viscosity, improving carotenoid solubility, and maintaining good stability. Moreover, a linear correlation was found between the color parameters and carotenoid contents. This study provides some guidance for screening suitable solvents for carotenoid extraction and storage.

Role of surface wetting on tribological behavior for laser nanotextured steel using ionic liquid lubricants

This research evaluates the effect of surface wettability on the tribological performance through ball-on-flat tribology testing. The substrate material, M2 tool steel, is laser processed and then functionalized with fluorocarbon and nitrile chemistry to achieve distinct oleophobicity and oleophilicity, respectively, but with a similar nanoscale surface texture. The baseline lubricant is poly-alpha-olefin (PAO) oil, and ionic liquids (ILs) are used as additives for this study. The interaction between the nanoscale textured steel surface and ionic liquid-based oils is investigated. A set of reciprocating wear tests are performed to investigate the tribological behavior of the tribo-system consisting of the surface-engineered, flat M2 tool steel specimen and a standard, surface-polished steel ball. Results show that the oleophobic flat surface results in a lower friction, while the oleophilic surface modification leads to a better wear protection to the flat surface. Ammonium-based IL provides the highest friction reduction, while the phosphonium-based ILs provide an improved wear protection.

Improving Co(II) separation from Ni(II) by solvent extraction using phosphonium-based ionic liquids

The solvent extraction of Co(II) from its aqueous solutions free of acids or chloride salts at high concentration by the ionic liquids trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate ([P66614][C272]) and trihexyl(tetradecyl)phosphonium thiocyanate ([P66614][SCN]) was characterised at saturation of the organic phase with Co(II) using toluene as diluent. The ionic liquids’ cation participated in the formation of two ion-pairs in the organic phase, i.e., one with the complex anion containing cobalt, and the other with the cobalt counter anion, thus preserving electroneutrality in both the organic and aqueous phases. This was considered to be an example of bifurcated extraction.UV–visible spectral studies of the intensively blue organic phase after Co(II) extraction demonstrated that the Co(II) coordination sphere geometry in the case of both extractants was tetrahedral. The Co(II) extraction stoichiometry was experimentally determined for the first time by saturating the organic phase with Co(II). The [P66614][C272] to Co(II) stoichiometric mole ratio in the extracted adduct was found to be 2.8:1, suggesting that eight phosphinate anions acted as bridging ligands around three cobalt centres. For the [P66614][SCN], the stoichiometric mole ratio was found to be 2.5:1 with the Co(II)-thiocyanate adduct consisting of two Co(II)-thiocyanate tetrahedra linked by a bridging thiocyanate ion.The Co(II) extraction was enhanced when the aqueous phase contained an anion with high lipophilicity (e.g., nitrate, thiocyanate). [P66614][SCN] did not extract Ni(II) from nitrate or chloride solutions, thus demonstrating its potential for the separation of Co(II) from Ni(II) without requiring the addition of high concentrations of acids or chloride salts to the aqueous phase.

Experimental Investigation of Tribological and Rheological Behaviour of Hybrid Nanolubricants for Applications in Internal Combustion Engines

In this study, the improvement in SAE 10W-40 engine oil tribological performance after the addition of magnesium oxide (MgO) nanoadditive and two different phosphonium-based ionic liquids (ILs) was investigated. Besides, the rheological behaviour of MgO-based nanolubricant and IL-based hybrid nanolubricants at the temperature range from 293.15 to 363.15 K was studied. The nanoparticle characterization was performed by means of transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The tribological properties, friction coefficients and wear parameters of the formulated oil modified with 0.01 wt% MgO and 1 wt% ILs compared with the neat 10W-40 oil were performed and analysed using a ball-on-three-pins tribometer and a 3D optical profilometer, respectively. Further analysis on the worn surface was shown by Raman spectroscopy and SEM images illustrating the formation of the protective IL and MgO tribo-films as hybrid additives. In friction tests with sliding steel-steel tribo-pairs, IL3-based hybrid nanolubricant decreased the coefficient of friction and wear volume by 7% and 59%, respectively, in comparison with the neat SAE 10W-40, hence better positive synergies were found for MgO and IL3 as hybrid additives. Interestingly, the thermophysical characterization by rheology also revealed that the nanoparticle and ionic liquids addition did not affect neither the viscosity response nor the Newtonian behaviour of the engine oil, adequately meeting the requirements for their use in internal combustion engines.Graphical

Processing Gray Selenium in Phosphonium-Based Ionic Liquids.

The dissolution of gray selenium in tetraalkylphosphonium acetate ionic liquids was investigated by UV-vis, NMR, and Raman spectroscopy as well as quantum chemical calculations and electrochemical methods. Acetate anions and tetraalkylphosphonium cations facilitate the formation and stabilization of oligoselenides Sen2- and cationic Se species in the ionic liquid phase. Chemical exchange of selenium atoms was demonstrated by variable-temperature 77Se NMR experiments. Additionally, uncharged cycloselenium molecules exist at high selenium concentrations. Upon dilution with ethanol, amorphous red selenium precipitates from the solution. Moreover, crystalline Se1-xTex solid solutions precipitate when elemental tellurium is added to the mixture as confirmed by powder X-ray diffraction and Raman spectroscopy.

Tribochemistry of imidazolium and phosphonium bis(oxalato)borate ionic liquids: Understanding the differences

Lubrication properties of imidazolium and phosphonium bis(oxalato)borate ionic liquids (ILs) are compared in a reciprocating sliding contact at 80 °C and 140 °C. Both the influence of the alkyl chain length and the cation architecture on friction, wear and lubricant breakdown are investigated. Imidazolium ILs showed lower friction than phosphonium ILs though only phosphonium-based ILs reduced wear. A longer alkyl chain reduced friction only in the case of the imidazolium-based ILs. Analysis of the wear scars was consistent with chemical breakdown solely of the anion. Chemical changes in the ILs after the tribotests were more pronounced for imidazolium-based ILs, and comparison of breakdown and tribofilm formation implicated catalysis by the imidazolium center, which, in turn, had a strong dependence on the surface self-assembly.

Tribological performance of ionic liquid impregnated porous aluminum borate ceramic

To achieve superior tribological performance without continuous lubricant supply, a novel ceramic - phosphonium based ionic liquids (P-ILs) system is developed via vacuum impregnation. The P-ILs with different viscosity and density impregnated in ceramic pellets were tested at different temperatures and sliding velocities. The results suggest that at a low temperature of 5 °C, the phosphonium benzoate and phosphonium salicylate IL exhibited a low coefficient of friction (COF) than the phosphonium saccharinate IL under a sliding velocity of 100 mm/s. Whereas this trend reversed at a higher temperature of 50 and 100 °C. Similar observations were also made for the wear rate of this unique system. It was found that the tribological performance of the P-IL+ceramic system depends on the thermal response of these ILs which is further correlated with the density and viscosity of P-ILs that control the supply of lubricants at the sliding interface.

High rate and long-term cycling of silicon anodes with phosphonium-based ionic liquids as electrolytes for lithium-ion batteries

This paper describes the effects of the length of the phosphonium alkyl chain in FSI-based ionic liquids (ILs) used as an electrolyte solvent with Si electrodes in a Li/Si half-cell. The electrochemical performance of Si nanoparticles at a high rate in the synthesized triethyl-n-butylphosphonium bis(fluorosulfonyl)imide) [P2224][FSI] and triethyl-n-octylphosphonium bis(fluorosulfonyl)imide) [P2228][FSI] ILs, which also contain 1 M LiFSI, is compared with that of a common organic electrolyte using either polyacrylic acid (PAA) or polyacrylonitrile (PAN) as a binder. For the three electrolytes, the highest performance was obtained with the PAN binder, while both electrodes in ILs exhibited superior performance compared to the conventional organic electrolyte. For the Si/PAN composite electrode, after 1000 cycles at 1 A.g−1, the delithiation capacities were 1344, 550 and 136 mAh.g−1 for [P2224][FSI] in 1 M LiFSI, [P2228][FSI] in 1 M LiFSI and the commercial organic electrolyte, which corresponded to capacity retentions of 61%, 50% and 5%, respectively. Our results indicate that the chemical structure of the phosphonium cation enabled the tuning of transport properties and significantly influences the electrochemical behavior of the Si anode in the presence of LiFSI/IL as an electrolyte.