Mixture Dimethyl Carbonate Research Articles

Contamination in LIB Pouch Cells Promoting Self‐Discharge and Crosstalk

AbstractStorage studies of lithium‐ion battery electrolyte within bags made of commercial pouch foils, commonly used as encasing material of battery cells, revealed the presence of contamination leaching from the pouch foil material into the electrolyte. By analyzing the stored electrolyte via GC‐MS the appearing compound was identified as 2,4‐di‐tert‐butylphenol (2,4‐DTBP). To investigate the influence of DTBP on the battery cell performance, full cells employing commercial LiNi1/3Mn1/3Co1/3O2 based cathodes and graphite‐type anodes were assembled using 1 M LiPF6 in ethylene carbonate/ dimethyl carbonate mixture as the electrolyte with/out the intentional addition of either 2,4‐DTBP or its constitutional isomer 2,6‐DTBP. Furthermore, dimethyl terephthalate (DMT), a literature known redox shuttle triggering impurity leaching from PET‐based fixing tape used in LIBs, was added to compare the effect of DMT to DTBPs. It was revealed that either DTBP contaminations have a significant impact on the self‐discharge behavior of the studied cells, which exceed the effect of present DMT. Moreover, all contaminants heavily increase transition metal dissolution‐migration‐deposition (TM DMD) processes and irreversible capacity loss. When vinylene carbonate, an SEI forming additive, is added to the electrolyte mixtures self‐discharge, as well as TM DMD are suppressed to a different degree depending on the type of contaminant added.

Thermophysical study for Binary mixtures of Dimethyl carbonate with Anisole, Butyl vinyl ether, Diisopropyl ether and Dibutyl ether at 303.15, 308.15 and 313.15 K

Ultrasonic velocity, density and viscosity have been determined for the binary compositions of dimethyl carbonate+ butyl vinyl ether, + diisopropyl ether, + anisole and + dibutyl ether at T= 303.15, 308.15 and 313.15 K. The inventive data is applied to assess the excess molar volume VmE, deviation in viscosity Δη and the acoustical parameters namely isentropic compressibility (Ks), free volume (Vf ), free length (Lf ) and internal pressure (πi). The excess or deviation properties are contoured to the Redlich-Kister polynomials and the outcomes are elucidated in terms of molecular interactions present in compositions.

Static layer melt crystallization of dimethyl carbonate: Binary thermodynamic phase diagram analysis and process optimization

Dimethyl carbonate (DMC) is one kind of important solvent for lithium battery electrolyte. The purifying method of DMC is crucial for obtaining high purity product of it. Using a green and sustainable technology makes more sense in the face of increasing environmental burdens. In this study, a static layer melt crystallization method was used to achieve the purification of high purity DMC from a mixture of DMC and its major impurities. The partial binary phase diagrams between DMC and the main impurity - methanol (MT) - were determined using differential scanning calorimetry (DSC) method. Effect of process parameters such as crystallization temperature, cooling rate, sweating temperature, and heating rate on the distribution coefficient Kf and yield Y were evaluated using One-factor-at-a-time (OFAT) experiment and response surface experiment, respectively. The phenomenological relationships between different parameters and distribution coefficient and yield were discussed and revealed. Eventually, under the optimized process conditions, the purity of DMC was increased from 96 % to 99.847 %, and the single yield could reach 70 %.

Efficient simulations of mobility matrices for electrolytes by applying forces.

Ion drift velocities in response to electric fields are a critical attribute of battery electrolytes. Accurately predicting species mobilities in such systems is an important challenge for atomistic simulations. In this work, we investigate two organic liquid electrolytes: LiPF6 dissolved in (a) dimethyl carbonate (DMC) and (b) a mixture of DMC and ethylene carbonate (EC). We compare two approaches to measure mobilities: observing center of mass diffusion with no forces applied, and observing species drift in response to external forces. The two approaches are related by the fluctuation-dissipation theorem, but they are not equally efficient computationally. We argue that statistical errors of the two methods scale differently with system size and simulation run time. In a head-to-head test, we apply both methods to LiPF6 in DMC in multiple simulations with the same size and run time. The drift method gives a much smaller variance in repeated measurements than the diffusion method, and should be preferred in practice.

Exploring the possibility of carbon neutral dimethyl carbonate production through urea alcoholysis processes

Dimethyl carbonate (DMC) is a green reactant that plays a crucial role in various industrial applications. In this study, the direct and indirect urea alcoholysis pathways for producing DMC from urea and methanol were simulated to assess their process performance and economic feasibility. The results showed that the highest energy consumption was in the separation of the azeotropic mixture of DMC and methanol. The indirect alcoholysis process was found to have lower energy consumption and lower carbon dioxide (CO2) emissions compared to conventional technology. The economic evaluation revealed that the indirect urea alcoholysis processes were economically feasible, with the price of methanol being the most significant factor affecting the economic performance. Despite these findings, the production of DMC from the urea and methanol pathways remains a challenge from an environmental perspective. Multiple sources of hydrogen for methanol production resulted in CO2 emissions ranging from 0.51 to 3.07 kg-CO2/kg-DMC. Although green hydrogen from electrolysis had the lowest CO2 emissions, it doubled the cost of DMC production over other hydrogens.

Vapor Equilibrium Data for the Binary Mixtures of Dimethyl Carbonate and Ethyl Methyl Carbonate in Compressed Carbon Dioxide

Phase equilibrium data (p, T, y) for the binary systems of carbon dioxide + dimethyl carbonate and carbon dioxide + ethyl methyl carbonate were obtained. All systems were measured for isotherms ranging from 298.2 K to 328.2 K with pressure ranging between 0.13 MPa and 10.6 MPa. A static equilibrium technique was established with samples quantified using an offline method. The results were modeled using the Peng–Robinson equation of state with van der Waals one-fluid mixing rules.Graphical

Microscopic mechanism study and process optimization of dimethyl carbonate production coupled biomass chemical looping gasification system

Biomass chemical looping gasification technology is one of the essential ways to utilize abundant biomass resources. At the same time, dimethyl carbonate can replace phosgene as an environment-friendly organic material for the synthesis of polycarbonate. In this paper, a novel system coupling biomass chemical looping gasification with dimethyl carbonate synthesis with methanol as an intermediate is designed through microscopic mechanism analysis and process optimization. Firstly, reactive force field molecular dynamics simulation is performed to explore the reaction mechanism of biomass chemical looping gasification to determine the optimal gasification temperature range. Secondly, steady-state simulations of the process based on molecular dynamics simulation results are carried out to investigate the effects of temperature, steam to biomass ratio, and oxygen carrier to biomass ratio on the syngas yield and compositions. In addition, the main energy indicators of biomass chemical looping gasification process including lower heating value and cold gas efficiency are analyzed based on the above optimum parameters. Then, two synthesis stages are simulated and optimized with the following results obtained: the optimal temperature and pressure of methanol synthesis stage are 150 °C and 4 MPa; the optimal temperature and pressure of dimethyl carbonate synthesis stage are 140 °C and 0.3 MPa. Finally, the pre-separation-extraction-decantation process separates the mixture of dimethyl carbonate and methanol generated in the synthesis stage with 99.11% purity of dimethyl carbonate. Above results verify the feasibility of producing dimethyl carbonate from the perspective of multi-scale simulation and realize the multi-level utilization of biomass resources.

Li-Ion Transport and Solvation of a Li Salt of Weakly Coordinating Polyanions in Ethylene Carbonate/Dimethyl Carbonate Mixtures.

Electrolytes with a high Li-ion transference number (tLi) have attracted significant attention for the improvement of the rapid charge-discharge performance of Li-ion batteries (LIBs). Nonaqueous polyelectrolyte solutions exhibit high tLi upon immobilization of the anion on a polymer backbone. However, the transport properties and Li-ion solvation in these media are not fully understood. Here, we investigated the Li salt of a weakly coordinating polyanion, poly[(4-styrenesulfonyl)(trifluoromethanesulfonyl)amide] (poly(LiSTFSA)), in various ethylene carbonate and dimethyl carbonate mixtures. The highest ionic conductivity was unexpectedly observed for the lowest polar mixture at the highest salt concentration despite the low dissociation degree of poly(LiSTFSA). This was attributed to a unique conduction phenomenon resulting from the faster diffusion of transiently solvated Li ions along the interconnected aggregates of polyanion chains. A Li/LiFePO4 cell using such an electrolyte demonstrated improved rate capability. These results provide insights into a design strategy of nonaqueous liquid electrolytes for LIBs.

Tale of a "Non-interacting" Additive in a Lithium-Ion Electrolyte: Effect on Ionic Speciation and Electrochemical Properties.

New lithium electrolytes compatible with high energy density cells are critical for lithium metal battery applications, but dendrite formation associated with the use of dilute organic electrolytes complicates their realization. High-concentration electrolytes mitigate some of the issues of the electrolytes but introduce additional problems, such as low conductivity and high cost. Hence, pseudo-concentrated electrolytes, wherein a co-solvent is added to a dilute electrolyte, have been presented as a possible alternative to both dilute and concentrated electrolytes. However, the effect that the co-solvent has on the electrolyte properties at both macroscopic and microscopic levels is unknown. Here, a study of the structure and electrochemical properties of two electrolytes as a function of co-solvent concentration is presented using an array of spectroscopies (FTIR, ATR–FTIR, and nuclear magnetic resonance) and computational methods (density functional theory calculations). The chosen electrolytes comprised two different lithium salts (LiPF6 and LiTFSI) in a mixture of dimethyl carbonate (DMC) with 1,1,1,3,3-pentafluorobutane (PFB) as the co-solvent. Our results show that in the case of the LiPF6/DMC electrolyte, the addition of a co-solvent (PFB) with a larger dielectric constant results in the strengthening of the lithium–anion interaction and the formation of aggregate species since PFB does not interact with the anion. Conversely, in the LiTFSI/DMC electrolyte, the co-solvent appears to interact with the anion via hydrogen bonds, which leads to the dissociation of contact ion pairs. The change in ionic speciation of the electrolytes upon addition of PFB provides a reasonable framework to explain the different trends in both the bulk and interfacial macroscopic properties, such as conductivity, viscosity, and electrochemical stability. Overall, our findings demonstrate that the interactions between the anion and the co-solvent must be taken into consideration when adding a co-solvent because they play a major role in determining the final electrolyte properties.

From the Direct Observation of a PAA‐Based Binder Using STEM‐VEELS to the Ageing Mechanism of Silicon/Graphite Anode with High Areal Capacity Cycled in an FEC‐Rich and EC‐Free Electrolyte

AbstractThe polymer binder is a key constituent of silicon‐based electrode formulation for lithium‐ion batteries. However, its extremely difficult visualization in fresh electrodes becomes completely impossible in cycled electrodes. Here, the combination of scanning transmission electron microscopy—valence electron energy‐loss spectroscopy with the use of a specific electrolyte solvent composition (a mixture of dimethyl carbonate and fluoroethylene carbonate, without ethylene carbonate) allows the visualization, for the first time, of the binder in silicon‐based electrodes, even cycled up to 100 cycles. Such an observation is possible as the only solid degradation product of this electrolyte is LiF, as confirmed by quantitative 7Li and 19F magic angle spinning nuclear magnetic resonance. The electrodes, based on a blend of silicon and graphite, have a very high surface capacity, 6.5 mAh cm−2, which makes them meaningful for electric vehicle applications. The performance is appreciable, in particular the first cycle efficiency approaching that of commercial graphite electrodes, as well as the capacity retention in full cell, versus LiNi0.5Mn0.3Co0.2O2, 60% after 100 cycles. This work also illustrates the ultimate state of destructuration of silicon after long cycling, which invites new ways of thinking about the design of this material.

Local approaches for electric dipole moments in periodic systems and their application to real-time time-dependent density functional theory.

Within periodic boundary conditions, the traditional quantum mechanical position operator is ill-defined, necessitating the use of alternative methods, most commonly the Berry phase formulation in the modern theory of polarization. Since any information about local properties is lost in this change of framework, the Berry phase formulation can only determine the total electric polarization of a system. Previous approaches toward recovering local electric dipole moments have been based on applying the conventional dipole moment operator to the centers of maximally localized Wannier functions (MLWFs). Recently, another approach to local electric dipole moments has been demonstrated in the field of subsystem density functional theory (DFT) embedding. We demonstrate in this work that this approach, aside from its use in ground state DFT-based molecular dynamics, can also be applied to obtain electric dipole moments during real-time propagated time-dependent DFT (RT-TDDFT). Moreover, we present an analogous approach to obtain local electric dipole moments from MLWFs, which enables subsystem analysis in cases where DFT embedding is not applicable. The techniques were implemented in the quantum chemistry software CP2K for the mixed Gaussian and plane wave method and applied to cis-diimide and water in the gas phase, cis-diimide in aqueous solution, and a liquid mixture of dimethyl carbonate and ethylene carbonate to obtain absorption and infrared spectra decomposed into localized subsystem contributions.

Lithium Borate Ester Salts for Electrolyte Application in Next‐Generation High Voltage Lithium Batteries

AbstractThe atmospheric instability and the corrosive tendency of hexafluorophosphate [PF6]− and fluorosulfonylimide [FSI]− based lithium salts, respectively, are among the major impediments towards their application as electrolytes in high voltage lithium batteries. Herein a new class of Li salts is introduced and their electrochemical behavior is explored. The successful synthesis and characterization are reported, including the crystal structure, of lithium 1,1,1,3,3,3‐(tetrakis)hexafluoroisopropoxy borate (LiBHfip). The oxidative stability of electrolytes of this salt in an ethylene carbonate:dimethyl carbonate mixture (v/v, 50:50) is found to be 5.0 V versus Li+/Li on various working electrodes, showing substantial improvement over a LiPF6 based electrolyte. Moreover, a high stability of an aluminum substrate is observed at potentials up to 5.8 V versus Li+/Li; in comparison, a LiFSI based electrolyte shows prominent signs of Al corrosion above 4.3 V versus Li+/Li. Cells tested with high voltage layered LiNi0.8Mn0.1Co0.1O2 (NMC811) and spinel LiMn2O4 (LMO) cathodes show stable cycling over 200 cycles with capacity retention of 76% and 90%, respectively. The LMO|Li cell maintains this same low capacity fade rate for 1000 cycles even after the salt has been exposed for 24 h to atmospheric conditions (water content ≈0.57 mass%).

Elucidating the mechanism behind the infrared spectral features and dynamics observed in the carbonyl stretch region of organic carbonates interacting with lithium ions.

Ultrafast infrared spectroscopy has become a very important tool for studying the structure and ultrafast dynamics in solution. In particular, it has been recently applied to investigate the molecular interactions and motions of lithium salts in organic carbonates. However, there has been a discrepancy in the molecular interpretation of the spectral features and dynamics derived from these spectroscopies. Hence, the mechanism behind spectral features appearing in the carbonyl stretching region was further investigated using linear and nonlinear spectroscopic tools and the co-solvent dilution strategy. Lithium perchlorate in a binary mixture of dimethyl carbonate (DMC) and tetrahydrofuran was used as part of the dilution strategy to identify the changes of the spectral features with the number of carbonates in the first solvation shell since both solvents have similar interaction energetics with the lithium ion. Experiments showed that more than one carbonate is always participating in the lithium ion solvation structures, even at the low concentration of DMC. Moreover, temperature-dependent study revealed that the exchange of the solvent molecules coordinating the lithium ion is not thermally accessible at room temperature. Furthermore, time-resolved IR experiments confirmed the presence of vibrationally coupled carbonyl stretches among coordinated DMC molecules and demonstrated that this process is significantly altered by limiting the number of carbonate molecules in the lithium ion solvation shell. Overall, the presented experimental findings strongly support the vibrational energy transfer as the mechanism behind the off-diagonal features appearing on the 2DIR spectra of solutions of lithium salt in organic carbonates.

Strategy for the Separation of the Mixture of Dimethyl Carbonate, Formaldehyde, and Water

In this work, the separation of a mixture of dimethyl carbonate (DMC), formaldehyde, and water is studied. In our process, formaldehyde is first extracted using water as the entrainer, and then the azeotrope of DMC–water is separated by extractive distillation with ethylene glycol. To verify the feasibility of the process, the liquid–liquid equilibrium (LLE) data of the DMC–formaldehyde–water system was measured and the vapor–liquid equilibrium (VLE) data of the DMC–ethylene glycol system was also measured at 101.3 kPa. Moreover, the reliability of experimental tie-line data was checked with the Bachman, Hand, and Othmer–Tobias equations, and the thermodynamic consistency of the measured VLE data was verified by the Van Ness test and infinite dilution test. Finally, all the measured values were correlated with the nonrandom two-liquid (NRTL) model and universal quasi-chemical (UNIQUAC) model, and the binary interaction parameters were regressed.

Synthesis and investigation of a new organic electrode material based on condensation product of triquinoyl with 1,2,4,5-tetraaminobenzene

Abstract We report on the synthesis of PTTA that is a product of polymeric condensation of triquinoyl with 1,2,4,5-tetraaminobenzene and on the application of this polymer as the redox-active material for an electrode in lithium-ion batteries. Two electrolytes were selected: 1 M LiPF6 in ethylene carbonate : dimethyl carbonate mixture (1 : 1) and the same electrolyte with the additive of benzo-15-crown-5 (5 wt%). The new organic electrode has a theoretical capacity of 344 mAh g−1 (3e−), and its redox processes have been investigated using CV, charge-discharge cycling, and quantum-chemical modeling. It was shown that added benzo-15-crown-5 allows achieving the theoretical discharge capacity under the same conditions. Quantum chemical DFT modeling provided insights into the mechanistic aspects of PTTA metallation.

Potential Analysis of a DMC/MeFo Mixture in a DISI Single and Multi-Cylinder Light Vehicle Gasoline Engine

<div class="section abstract"><div class="htmlview paragraph">In this study a mixture of dimethyl carbonate (DMC) and methyl formate (MeFo) was used as a synthetic gasoline replacement. These synthetic fuels offer CO<sub>2</sub>-neutral mobility if the fuels are produced in a closed CO<sub>2</sub>-cycle and they reduce harmful emissions like particulates and NO<sub>X</sub>. For base potential investigations, a single-cylinder research engine (SCE) was used. An in-depth analysis of real driving cycles in a series 4-cylinder engine (4CE) confirmed the high potential for emission reduction as well as efficiency benefits.</div><div class="htmlview paragraph">Beside the benefit of lower exhaust emissions, especially NO<sub>X</sub> and particle number (PN) emissions, some additional potential was observed in the SCE. During a start of injection (SOI) variation it could be detected that a late SOI of DMC/MeFo has less influence on combustion stability and ignitability. With this widened range for the SOI the engine application can be improved for example by catalyst heating or stratified mode. Furthermore, until λ = 0.8 no significant PN increase was noted in contrast to gasoline. This is also a positive capability for combustion modes with local rich areas in the mixture. From the experience of previous investigations, the synthetic fuels’ high knock-resistance potential enabled an increase in the compression ratio (CR) from epsilon ~ 11 to ~ 15 to enhance the indicated efficiency.</div><div class="htmlview paragraph">In general, in the 4CE the positive effects of DMC/MeFo on harmful emissions were confirmed. Even in the series configuration, the brake efficiency increased by 16 % at maximum low-end torque compared to gasoline. The increased in-cylinder cooling and the lower laminar flame temperature by the DMC/MeFo implies lower maximum exhaust temperatures. Therefore, a stoichiometric mixture could be used over the whole engine map. During the legislative driving cycles, for example WLTC, the PN, NO<sub>X</sub>, CO and CH<sub>4</sub> emissions decreased by 50 % or more.</div><div class="htmlview paragraph">In summary, oxygenated fuel opens great opportunities for replacing fossil fuel in gasoline engine applications.</div></div>

Identification of In-Cylinder Aerosol Flow Induced Emissions due to Piston Ring Design in a DISI Single Cylinder LV Engine Using Oxygenated Synthetic Fuels

<div class="section abstract"><div class="htmlview paragraph">In the near future, pollutant and GHG emission regulations in the transport sector will become increasingly stringent. For this reason, there are many studies in the field of internal combustion research that investigate alternative fuels, one example being oxygenated fuels. Additionally, the design of engine components needs to be optimized to improve the thresholds of clean combustion and thus reduce particulates. Simulations based on PRiME 3D® for dynamic behaviors inside the piston ring group provide a guideline for experimental investigation. Gas flows into the combustion chamber are controlled by adjusting the piston ring design. A direct comparison of regular and synthetic fuels enables to separate the emissions caused by oil and fuel. This study employed a mixture of dimethyl carbonate (DMC) and methyl formate (MeFo). These two components have no C-C bonds, and the mixture displayed extremely good performance in terms of the particle number (PN) emissions on an ambient level published in previous studies. This fuel property is employed in this study to identify oil induced, engine-out PN-emissions, while the combustion process remains almost identical to that of conventional gasoline. The PN-emissions are measured and subdivided into two ranges: larger than 10 nm and larger than 23 nm.</div><div class="htmlview paragraph">It was demonstrated that merely changing the piston ring design has an impact on raw PN engine emissions and gas flow behavior in the piston assembly. An increase in PN-emissions and lower blow-by level could only be detected by changing the piston ring design. With reduced, predicted fluid flows into the combustion chamber, lower VOC emissions could be observed during motored runs. The adaptations in the tested piston ring design demonstrate that it is possible to improve particulate emissions by modifying the piston ring group.</div></div>

Densities and viscosities for binary mixtures of dimethyl carbonate with 1-heptanol, 1-octanol, 1-nonanol, and 1-decanol

In this work, the density and viscosity data for binary mixtures of dimethyl carbonate with 1-heptanol, 1-octanol, 1-nonanol, and 1-decanol were presented from 303.15 K to 333.15 K at atmospheric pressure over different concentration ranges. The density and viscosity measurement was carried out based on the vibrating-tube densimeter and Ubbelohde capillary viscometer, respectively. Derived properties, such as excess molar volumes and viscosity deviations, were calculated from the experimental values, and were correlated based on the Redlich-Kister equation. In addition, excess molar volumes and viscosity deviations of the studied mixtures were analyzed and compared with other DMC/1-alcohols mixtures reported in the literatures.

Molecular Dynamics Simulation and Experimental Study of Tribological Behavior of Dimethyl Carbonate–Diesel Blends in Synthetic Base Oil

Oxygenated fuel is recognized as an effective alternative fuel for the petrochemical industry. Studies have shown that using a mixture of dimethyl carbonate (DMC) and diesel fuel can help reduce soot emissions. Due to incomplete combustion of some diesel fuel, a small amount of fuel will inevitably enter to the engine oil and cause engine oil dilution. Herein, the tribological properties of DMC–diesel blends in different base oils are investigated for the first time using ball-on-disc tribotests and molecular dynamics (MD) simulation. The experiments combined with MD simulation show that the trimellitate and alkyl naphthalene can effectively inhibit the deterioration of friction and wear characteristics caused by engine oil dilution. Analysis results revealed that the benzene ring structure and long chain of trimellitate and alkyl naphthalene have higher adsorption energy on the Fe (110) and can form an adsorption film to resist the deterioration due to fuel dilution. The findings offer a new potential application of oxygenated fuel in lubrication and tribology.

Improving the viscosity and density of n-butanol as alternative to gasoline by blending with dimethyl carbonate

n-Butanol is a promising alternative to gasoline, but has the defect of high viscosity, while dimethyl carbonate (DMC), which is a good additive for gasoline to improve the combustion efficiency, has low viscosity. In this work, DMC is used as additive to reduce the viscosity of n-butanol. The viscosities of DMC + n-butanol binary mixtures were measured from 313.15 K to 343.15 K and at pressures up to 15 MPa over the mole fractions from 0.1 to 0.9. The densities of the mixtures were also measured to check the effect of DMC on the density of n-butanol. Experimental results show that DMC can greatly reduce viscosity, and meanwhile increase the density, which is expected to improve the performance of n-butanol as the alternative to gasoline. The dependence of the improvement of the density and viscosity of n-butanol caused by adding DMC on temperature and pressure are investigated to guide the optimization of combustion process. Two models were proposed for the calculation of the viscosities and densities of the binary mixtures of DMC and n-butanol with the average absolute relative deviations of 0.09% and 2.58%, respectively.