Carbonate Solvents Research Articles

BMIm][BARF] imidazolium salt solutions in alkyl carbonate solvents: Structure and interactions

Solutions of weakly coordinating ionic liquids (ILs) in alkyl carbonates are gaining growing attention, as the latter are “green” solvents with high solvation power, but the phase behavior and structure of ILs in organic polar solvents are still poorly understood. Here, we study the interactions and nanoscale structure of 1‑butyl‑3-methylimidazolium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, [BMIm][BARF], in three symmetrical alkyl carbonate solvents with increasing alkyl chain-length. Electrical conductivity and nuclear magnetic resonance measurements showed that [BMIm][BARF] was mostly undissociated in these solvents, especially at lower IL concentration. Small angle X-ray scattering patterns evidenced the presence of rod-like nanostructures in the IL/solvent mixtures. At higher IL concentration, [BMIm][BARF] is increasingly more dissociated in solvents with lower dielectric constant, as confirmed by analysis of the solvents’ carbonyl stretching band via Fourier transform infrared spectroscopy. This trend is opposite to that exhibited by BMIm ILs with less bulky counterions. The bulky BARF− is weakly coordinating and has no ability to give strong H-bonding, thus short-range anisotropic van der Waals forces are likely key in the interaction of the ion pairs. The slower self-diffusion of the ions in alkyl carbonates with lower dielectric constants might partially hinder close contact needed for self-assembly into local nano-sized structures. Overall, our results shed light on interactions and self-organization in imidazolium salt-alkyl carbonate mixtures, with potential impact in applicative fields spanning from batteries, catalysis and extraction, up to bio-applications (antimicrobial and bioengineering).

Efficient sampling of TrkA transmembrane domain dimerization captures functionally distinct structural ensembles.

Upon ligand binding, the transmembrane domains (TMD) of the receptor tyrosine kinase (RTK) dimerize, induce conformational change in the juxtamembrane domain (JMD), and trigger downstream phosphorylation that eventually determines fate of the cell. To overcome the experimental difficulty in probing the TMD dimerization events in membrane bilayers, we employed all-atom molecular dynamics with a novel membrane mimetic solvent Simple Carbon Solvent Ethane (SCSE) to efficiently sample the TMD dimerization processes for tropomyosin receptor kinase A (TrkA). Spontaneous and stable TMD dimers were observed in less than 50 ns of simulation time from an initially separated grid configuration. We then performed hierarchical clustering using a customized distance metric based on TMD contact residues, and revealed major structural ensembles of TMD dimers. We demonstrated the validity of the resolved TMD dimer structures by performing MM-GBSA free energy calculation and molecular dynamics with full-tail lipid bilayers. As the residues in contact in the most populated TMD dimer ensemble from our SCSE simulations overlap with those found to be critical for kinase activation, we hypothesized that the captured TMD dimer corresponds to the active state, while the previously characterized NMR structure is the inactive state. To understand the role of different TMD dimer conformations in downstream signaling, we assembled TMD+JMD constructs using the captured in simulation dimer structure and the NMR structure. We modelled the system with Highly Mobile Membrane Mimetic (HMMM) for accelerated peptide-lipid interactions and found that the captured TMD dimer leads to JMD conformations distinct from those tethered to the NMR dimer structure, which may enable the kinase domain for cross-phosphorylation. Our method represents a new approach to study RTK dimerization and sample physiologically relevant dimer structures.

Nonflammable Electrolyte Based on Fluoroethylene Carbonate for High-Voltage LiCoO2/Si–Graphite Lithium-Ion Batteries

An electrolyte for high-voltage LiCoO2/Si–graphite pouch cells is proposed in this work, which is composed of LiPF6 salt and fluoroethylene carbonate solvent as well as tris(trimethylsilyl) phosphate and (ethoxy)pentafluorocyclotriphosphazene additives. Tris(trimethylsilyl) phosphate additive plays a role in improving the interfacial properties of electrodes, and (ethoxy)pentafluorocyclotriphosphazene additive makes this electrolyte nonflammable. Its conductivity is as high as 5.48 mS cm–1 at 25 °C. This safe electrolyte also enables the high-voltage LiCoO2/Si–graphite pouch cells to obtain the ideal electrochemical performances. At room temperature, the capacity retention reaches 81.7% after 200 cycles at 1C, and the discharge capacity at 3C still retains about 77% of the capacity at 1C. Furthermore, the interfacial properties of electrodes are analyzed by scanning electron microscopy and X-ray photoelectron spectroscopy measurements.

Optimal Blend between Carbonate Solvents and Fluoroethylene Carbonate for High-Voltage and High-Safety Li(Ni0.8Mn0.1Co0.1)O2 Lithium-Ion Cells

Optimal Blend between Carbonate Solvents and Fluoroethylene Carbonate for High-Voltage and High-Safety Li(Ni_0.8Mn_0.1Co_0.1)O₂ Lithium-Ion Cells

A comparative analysis of volumetric, viscometric and conductometric properties of Triethylmethylammonium Tetrafluoroborate (TEMABF4) and Tetraethylammonium Tetrafluoroborate (TEABF4) in pure propylene carbonate (PC) and binary aqueous propylene carbonate solvents

Electrolytes play a major role in electrochemical energy storage devices and specifically organic electrolytes are used predominantly over aqueous electrolytes due to wide electrochemical window, high energy density and efficiency. However, aqueous electrolytic systems for energy storage applications still need to be explored as these are non-flammable, environment friendly, non-toxic, carrying high ionic conductivity and low cost as compared to organic counterparts. In this study, an effort has been made in doing a comparative analysis of the physicochemical properties of Triethylmethylammonium Tetrafluoroborate (TEMABF4) and Tetraethylammonium Tetrafluoroborate (TEABF4) in pure propylene carbonate (PC) and binary aqueous mixtures of PC (0.01 &0.02 m) at different temperatures and concentrations. From this data, various volumetric, viscometric, and conductometric parameters have been calculated and the results obtained are analysed and compared in terms of solute–solute and solute–solvent interactions. From the analysis of thermo physical parameters, we have found that both the salts act as structure breaker in PC whereas structure maker in binary aqueous mixtures of PC (0.01 & 0.02 m). FTIR studies have also been done to see the intermolecular interactions and structural alterations. Furthermore, results from Cyclic Voltammetry (CV) studies suggested that a binary aqueous organic electrolytic system can also be a potential electrolytic system as its electrochemical window is comparable to that of pure electrolytic organic solvents.

In Situ Neutron Reflectometry Study of a Tungsten Oxide/Li-Ion Battery Electrolyte Interface.

The solid electrolyte interface/interphase (SEI) is of great importance to the viable operation of lithium-ion batteries. In the present work, the interface between a tungsten oxide electrode and an electrolyte solution consisting of LiPF6 in a deuterated ethylene carbonate/diethyl carbonate solvent was characterized with in situ neutron reflectometry (NR) at a series of applied electrochemical potentials. NR data were fit to yield neutron scattering length density (SLD) depth profiles in the surface normal direction, from which composition depth profiles were inferred. The goals of this work were to characterize SEI formation on a model transition-metal oxide, an example of a conversion electrode, to characterize the lithiation of WO3, and to help interpret the results of an earlier study of tungsten electrodes without an intentionally grown surface oxide. The WO3 electrode was produced by thermal oxidation of a W thin film. Co-analysis of NR and X-ray reflectivity data indicated that the stoichiometry of the thermal oxide was WO3. As the electrode was polarized to progressively more reducing potentials, starting from open circuit and down to +0.25 V versus Li/Li+, the layer that was originally WO3 expanded and increased in lithium content. The reduced electrode consisted of two to three layers: an inner layer (the evolving conversion electrode) which may have been mixed W and Li2O and unreacted WO3 or LixWO3, a layer rich in protons and/or lithium, possibly corresponding to LiOH or LiH (the inner SEI), and an outermost layer adjacent to the solution with an SLD close to that of the solution, possibly consisting of lower SLD species with solution-filled porosity or deuteron-rich species derived from the solvents (the outer SEI), though the presence of this layer was tenuous. For the steps in the direction of more oxidizing potentials, the evolution of the layer structure was qualitatively the reverse of that seen when stepping toward more negative potentials, though with hysteresis. The SLD gradient suggested that the reaction was not limited by diffusion within the film. No clear phase boundary was evident in the evolving conversion electrode.

The Electrochemical Stabilization of Silicon Anodes via a Locally Concentrated LiNO3 Complex

The solid electrolyte interphase (SEI) plays an integral role in regulating the stability of lithium-ion batteries, particularly those employing next-generation anode materials like lithium (Li)-metal or silicon (Si). Herein, a locally concentrated additive framework is designed to incorporate a LiNO3 sacrificial additive into conventional carbonate-containing electrolytes to heighten electrochemical stability in such systems. Though LiNO3 is effectively insoluble in carbonate solvents, it is introduced in moderate amounts to the electrolyte in the form of a highly concentrated diglyme complex, which is then dispersed and diluted throughout the bulk carbonate electrolyte in a homogenous, liquid, phase-stable solution. The addition of this additive complex considerably enhances the electrochemical stability of 4 V systems containing Li-metal or Si anodes over the course of cycling as well as during potentiostatic holds. It is shown that the sacrificial reduction of LiNO3 leads to the formation of favorable nitrogen-containing species on the surface of Si, like what is known to occur with Li-metal. However, the initial deposition of these products is found to transform the SEI towards having greater inorganic character overall, with significantly more embedded LiF throughout. These insights expand our understanding of electrolyte and SEI design for electrochemically resilient next-generation anode systems.

First-principles study of sodium adsorption on defective graphene under propylene carbonate electrolyte conditions.

Hard carbon (HC) has been predominantly used as a typical anode material of sodium-ion batteries (SIBs) but its sodiation mechanism has been debated. In this work, we investigate the adsorption of Na atoms on defective graphene under propylene carbonate (PC) and water solvent as well as vacuum conditions to clarify the sodiation mechanism of HC. Within the joint density functional theory framework, we use the nonlinear polarizable continuum model for PC and the charge-asymmetric nonlocally-determined local electric solvation model for water. Our calculations reveal that the centre of each point defect such as mono-vacancy (MV), di-vacancy (DV) and Stone-Wales is a preferable adsorption site and the electrolyte enhances the Na adsorption through implicit interaction. Furthermore, we calculate the formation energies of multiple Na atom arrangements on the defective graphene and estimate the electrode potential versus Na/Na+, verifying that the multiple Na adsorption on the MV and DV defective graphene under the PC electrolyte conditions is related to the slope region of the discharge curve in HC. This reveals new prospects for optimizing anodes and electrolytes for high performance SIBs.

Optimising the electrochemical reduction of CO2 to oxalic acid in propylene carbonate

Herein, carbon dioxide electroreduction to oxalate/oxalic acid in a propylene carbonate solvent system, catalysed by the addition of benzonitrile is reported.

New method for graphitizing polyurethane (PU) prepolymers over cellulose fiber surface and physical properties assessment on cementitious composites

A new method to graft polyurethane groups on cellulose fiber surface in a propylene carbonate medium, followed by a washing step with methylene chloride is proposed. The synthesis process in propylene carbonate solvent medium is an effective and straightforward way to graft polyurethane prepolymers on cellulose fibers. Reaction was carried out in non-pressurized vessels and low temperature (60 °C). The cleaning step proposed with methylene chorine solvent was effective as no signal of isocyanate group (NCO) was found on Fourier-transform infrared spectroscopy performed on grafted fibers. X-ray photoelectron spectroscopy results from cellulose modified fibers show the presence of nitrogen and a corresponding increase in CC bonds on the cellulose surface, which suggests that polyurethane prepolymer was successfully grafted on fiber surfaces. Secondary ion mass spectrometry images collected from polyurethane grafted fibers indicate that the isocyanate is uniformly distributed on the cellulose modified with PAPI™ 27 Polymeric MDI. Application tests carried out on fiber cement composites showed promising results. PAPI™ 27 Polymeric MDI grafted on the cellulose fibers surface has reduced the water absorption on fiber cement composites by approximately 15 % (p < 0.05) compared to composites prepared with non-modified cellulose fibers. Nevertheless, further exploration on fiber cement composite application is required to understand the impact of the cellulose treatment on the mechanical properties, fiber preservation and overall durability aspects.

Physical properties, antioxidant capacity, and starch digestibility of cookies enriched with steam-exploded wheat bran.

Wheat bran-based food is rich in bioactive compounds, and steam explosion enhances the nutritional properties of wheat bran. This study examined the potential utilization of steam-exploded wheat bran (SWB) in cookie formulation. The influence of steam explosion on the chemical compounds in wheat bran and the effects of SWB on the physical properties, antioxidant capacity, and starch digestibility of cookies were investigated. The results showed that steam explosion facilitated the release of reducing sugar, flavonoids, phenolic substances, and amino acid nitrogen in wheat bran, thereby improving its nutritional properties. The reduction of sugar, total flavonoids, total phenolics, and amino acid nitrogen contents of wheat bran after steam explosion increased by 34.22, 183.02, 284.09, and 93.39%, respectively, compared with those of native wheat bran. Substitution of SWB for wheat flour mainly induced higher water, sodium carbonate, and sucrose solvent retention capacities, which were positively related to the spread ratio and hardness of cookies. The cookies with more SWB substitution (30-50%) expressed a higher spread ratio and harder texture than the others. The substitution of SWB caused changes in the antioxidant properties of cookies, which were related to the phenolic content. The cookies with SWB showed a higher DPPH radical scavenging activity (16.30-30.93%) than that of the control (14.74%). SWB might form a matrix barrier to hinder starch digestion, thus reducing the digestibility of cookies. The cookies enriched with 30-50% of the SWB exhibited greater physical properties and antioxidant capacity but lower starch digestibility than those of other cookies. The results will contribute to expanding the application range and improving the quality of bran-rich flour products.

HPHT Crystallization of Diamond on Seed with Use of Carbon Solvents Prepared by Powder Metallurgy Methods

HPHT Crystallization of Diamond on Seed with Use of Carbon Solvents Prepared by Powder Metallurgy Methods

Novel and Highly Sensitive Electrochemical Sensor for the Determination of Oxytetracycline Based on Fluorine-Doped Activated Carbon and Hydrophobic Deep Eutectic Solvents.

Residues of oxytetracycline (OTC), a veterinary antibiotic and growth promoter, can be present in animal-derived foods; their consumption is harmful to human health and their presence must therefore be detected and regulated. However, the maximum residue limit is low, and consequently highly sensitive and accurate detectors are required to detect the residues. In this study, a novel highly sensitive electrochemical sensor for the detection of OTC was developed using a screen-printed electrode modified with fluorine-doped activated carbon (F-AC/SPE) combined with a novel deep eutectic solvent (DES). The modification of activated carbon by doping with fluorine atoms (F-AC) enhanced the adsorption and electrical activity of the activated carbon. The novel hydrophobic DES was prepared from tetrabutylammonium bromide (TBABr) and a fatty acid (malonic acid) using a green synthesis method. The addition of the DES increased the electrochemical response of F-AC for OTC detection; furthermore, it induced preconcentration of OTC, which increased its detectability. The electrostatic interactions between DES and OTC as well as the adsorption of OTC on the surface of the modified electrode through H-bonding and π-π interactions helped in OTC detection, which was quantified based on the decrease in the anodic peak potential (E pa = 0.3 V) of AC. The electrochemical behavior of the modified electrode was investigated by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. Under optimum conditions, the calibration plot of OTC exhibited a linear response in the range 5-1500 μg L-1, with a detection limit of 1.74 μg L-1. The fabricated electrochemical sensor was successfully applied to determine the OTC in shrimp pond and shrimp samples with recoveries of 83.8-100.5% and 93.3-104.5%, respectively. In addition to the high sensitivity of OTC detection, the proposed electrochemical sensor is simple, cost-effective, and environmentally friendly.

Electrochemical Study on Mixture of 1M LiPF6 and Carbonate Solvents as an Electrolyte in Graphite/ Lithium and Graphene/ Lithium-Ion Batteries

Electrochemical Study on Mixture of 1M LiPF6 and Carbonate Solvents as an Electrolyte in Graphite/ Lithium and Graphene/ Lithium-Ion Batteries

Organofluorophosphates as Oxidative Degradation Products in High-Voltage Lithium Ion Batteries with NMC or LNMO Cathodes

Organofluorophosphates (OFPs) have been reported to pose substantial health hazards due to their structural similarities to pesticides and nerve agents. Formation of OFPs in lithium ion batteries (LIBs) due to hydrolysis of the conducting salt lithium hexafluorophosphate (LiPF6) and the reaction with the organic carbonate solvents that make up the electrolyte has been discussed in literature. The oxidative formation of OFPs in electrolytes containing fluoroethylene carbonate (FEC) and vinylene carbonate (VC) as film-forming additives is presented in this study. Further the impact of potentially reactive positive electrode surfaces is investigated with the layered metal oxide NCM622 which is ascribed to release reactive oxygen species at high voltages and the spinel type LNMO as a typical high-voltage material. Cycling of the self-assembled LIB coin cells (CR2032) at cut-off voltages of 4.8 V gave rise to a number of degradation products including potentially highly toxic OFPs. Here, the presence of the film-forming additive had a massive impact on the amount of OFPs formed during electrochemical cycling experiments, which raises further concerns for the utilization of film-forming additives for high voltage applications. The formation pathway of OFPs through EC-polymerization proposed in literature is evaluated and an alternative mechanism with FEC/VC as the carbonyl carbon-donor is presented. Structure elucidation and separation of the formed OFPs is achieved by utilization of reversed-phase (RP) chromatography hyphenated to a high-resolution ion trap time-of-flight mass spectrometer (IT-TOF-MS). The findings presented in this study support further investigation of the formation of OFPs in film-forming additive-containing electrolytes, quantitative approaches and toxicological assessments due to the highly toxic nature of OFPs.

All-climate outstanding-performances lithium-ion batteries enabled by in-situ constructed gel polymer electrolytes

Lithium-ion batteries (LIBs) with gel polymer electrolytes (GPE) employing highly volatile and extremely flammable linear carbonate solvents still face the safety hazard of fire and combustion. Gamma-butyrolactone (GBL) as electrolyte solvent can greatly improve the safety and all-climate performance of LIBs due to its higher flash point, lower vapor pressure, better thermal stability and wider liquid temperature range than those of the carbonate solvents. However, the application of GBL solvent is hindered by its incompatibility with the most widely used graphite anode. Herein, an all-climate high-power LiMn2O4 + LiMn0.7Fe0.3PO4/graphite pouch cell is achieved by employing non-flammable GBL-based GPE. The interphacial instability of GBL/graphite is solved by introducing three synergistic film-forming additives, including lithium bis(oxalato)borate, 4-vinyl-1,3-dioxolan-2-one and 3-sulfolene. The developed non-flammable GBL-based GPE enables the all-climate high-power LIBs application with great room-temperature rate capability, excellent low-temperature cranking and long elevated-temperature durability. More importantly, the developed pouch cells exhibit excellent cold-cranking performance even at −18 °C and maintain a high-capacity retention of 80 % after 400 cycles at 1C at 25 °C.

Constructing Stable Anion-Tuned Electrode/Electrolyte Interphase on High-Voltage Na3 V2 (PO4 )2 F3 Cathode for Thermally-Modulated Fast-Charging Batteries.

Constructing stable electrode/electrolyte interphase with fast interfacial kinetics is vital for fast-charging batteries. Herein, we investigate the interphase that forms between a high-voltage Na3 V2 (PO4 )2 F3 cathode and the electrolytes consisting of 3.0, 1.0, or 0.3 M NaClO4 in an organic carbonate solvent (47.5 : 47.5 : 5 mixture of EC: PC: FEC) during charging up to 4.5 V at 55 °C. It is found that a higher anion/solvent ratio in electrolyte solvation structure induces anion-dominated interphase containing more inorganic species and more anion derivatives (Cx ClOy ), which leads to a larger interfacial Na+ transport resistance and more unfavorable gas evolution. In comparison, a low anion/solvent ratio derives stable anion-tuned interphase that enables better interfacial kinetics and cycle ability. Importantly, the performance of a failed cathode is restored by triggering the decomposition of Cx ClOy species. This work elucidates the role of tuning interphase in fast-charging batteries.

Constructing Stable Anion‐Tuned Electrode/Electrolyte Interphase on High‐Voltage Na 3 V 2 (PO 4 ) 2 F 3 Cathode for Thermally‐Modulated Fast‐Charging Batteries

Constructing stable electrode/electrolyte interphase with fast interfacial kinetics is vital for fast-charging batteries. Herein, we investigate the interphase that forms between a high-voltage Na3V2(PO4)2F3 cathode and the electrolytes consisting of 3.0, 1.0, or 0.3 M NaClO4 in an organic carbonate solvent (47.5:47.5:5 mixture of EC: PC: FEC) during charging up to 4.5 V at 55oC. It is found that a higher anion/solvent ratio in electrolyte solvation structure induces anion-dominated interphase containing more inorganic species and more anion derivatives (CxClOy), which leads to a larger interfacial Na+ transport resistance and more unfavorable gas evolution. In comparison, a low anion/solvent ratio derives stable anion-tuned interphase that enables better interfacial kinetics and cycle ability. Importantly, the performance of a failed cathode is restored by triggering the decomposition of CxClOy species. This work elucidates the role of tuning interphase in fast-charging batteries.

Theoretical Consideration of Side Reactions between the VS&lt;sub&gt;4&lt;/sub&gt; Electrode and Carbonate Solvents in Lithium–metal Polysulfide Batteries

Theoretical Consideration of Side Reactions between the VS&lt;sub&gt;4&lt;/sub&gt; Electrode and Carbonate Solvents in Lithium–metal Polysulfide Batteries

Correlation between Redox Potential and Solvation Structure in Biphasic Electrolytes for Li Metal Batteries.

The activity of lithium ions in electrolytes depends on their solvation structures. However, the understanding of changes in Li+ activity is still elusive in terms of interactions between lithium ions and solvent molecules. Herein, the chelating effect of lithium ion by forming [Li(15C5)]+ gives rise to a decrease in Li+ activity, leading to the negative potential shift of Li metal anode. Moreover, weakly solvating lithium ions in ionic liquids, such as [Li(TFSI)2 ]- (TFSI = bis(trifluoromethanesulfonyl)imide),increase in Li+ activity, resulting in the positive potential shift of LiFePO4 cathode. This allows the development of innovative high energy density Li metal batteries, such as 3.8V class Li | LiFePO4 cells, along with introducing stable biphasic electrolytes. In addition, correlation between Li+ activity, cell potential shift, and Li+ solvation structure is investigated by comparing solvated Li+ ions with carbonate solvents, chelated Li+ ions with cyclic and linear ethers, and weakly solvating Li+ ions in ionic liquids. These findings elucidate a broader understanding of the complex origin of Li+ activity and provide an opportunity to achieve high energy density lithium metal batteries.