Glycol Dimethyl Ether Research Articles

Conceptual design, techno-economic and environmental evaluation of a coal-based polygeneration process for ethylene glycol and polymethoxy dimethyl ethers production

Coal-based polygeneration technology is regarded as a promising alternative to utilize coal more efficiently and cleanly. In this study, a novel coal-based polygeneration process for ethylene glycol and polymethoxy dimethyl ethers production (CtE&D) is investigated and compared with the standalone reference system. The whole flowsheet of the CtE&D process is simulated firstly to establish its material and exergy balance, water balance, steam balance, and element balance. A detailed technical, economic, and environmental analysis is conducted to manifest the advantages of the CtE&D process. Compared with the standalone reference system, results show that the novel CtE&D process is promising since it increases the exergy efficiency by 2.11%, saves the total capital investment and total production cost by 7.52% and 5.52%, and improves the net present value by 262M$. Moreover, it reduces the CO2 emissions, wastewater, and solid waste emissions by 2.97%, 4.15%, and 2.84%, respectively. This paper provides a new direction for clean and efficient utilization of coal resources, and supplies a set of evaluation method for polygeneration systems from technical, economic, and environmental viewpoints.

Environmentally Friendly Lithium-Terephthalate/Polylactic Acid Composite Filament Formulation for Lithium-Ion Battery 3D-Printing via Fused Deposition Modeling

In this paper, the development of an environmentally-friendly lithium-terephtalate/polylactic acid (Li2TP/PLA) composite filament, for its use, once 3D-printed via Fused Deposition Modeling (FDM), as negative electrode of a lithium-ion battery is reported. Solvent-free formulation of the 3D-printable filament is achieved through the direct introduction of synthesized Li2TP particles and PLA polymer powder within an extruder. Printability is improved through the incorporation of poly(ethylene glycol) dimethyl ether average Mn∼500 (PEGDME500) as plasticizer, while electrical performances are enhanced through the introduction of carbon black (CB). Thermal, electrical, morphological, electrochemical and printability characteristics are discussed thoroughly. By taking advantage of the 3D-printing slicer software capabilities, an innovative route is proposed to improve the liquid electrolyte impregnation within the 3D-printed electrodes.

An Attempt to Formulate Non‐Carbonate Electrolytes for Sodium‐Ion Batteries

AbstractNon‐aqueous carbonate solvents have been the main choice for the development of lithium‐ion batteries, and similarly most research on sodium‐ion batteries have been performed using carbonate‐based solvents. However, the differences between sodium and lithium batteries – in term chemistry/electrochemistry properties as well as electrode materials used – open up opportunities to have a new look at solvents that have attracted little attention as electrolyte solvent. This work investigates properties of a wide range of different solvent classes in the context of sodium‐ion battery electrolytes and compares them to the performance of propylene carbonate. The thirteen solvents studied here include one or several members of glymes, carbonates, lactones, esters, pyrrolidones, sulfones, and alkyl phosphates. Out of those, five outperforming solvents of γ‐butyrolactone (GBL), γ‐valerolactone (GVL), N‐methyl‐2‐pyrrolidone (NMP), propylene carbonate (PC), and trimethyl phosphate (TMP) were further investigated using additives of ethylene sulfite (ES), vinylene carbonate (VC), fluoroethylene carbonate (FEC), prop‐1‐ene‐1,3‐sultone (PES), sulfolane (TMS), tris(trimethylsilyl) phosphite (TTSPI), and sodium bis(oxalato)borate (NaBOB). The solvents TMS and tetraethylene glycol dimethyl ether (TEGDME) were tested in 1 : 1 mixtures by volume with the co‐solvents; NMP, dimethoxyethane (DME), and TMP. All electrolytes used NaPF6 as the salt. Primary evaluation relied on electrochemical cycling of full‐cell sodium‐ion batteries consisting of Prussian white cathodes and hard‐carbon anodes. Galvanostatic cycling was performed using both two‐ and three‐electrode cells, in addition, cyclic and linear sweep voltammetry was used to further evaluate the electrolyte formulations. Moreover, the resistance was measured on the anode and cathode, using Intermittent current interruption (ICI) technique.

Poly(ethylene glycol) dimethyl ether mediated oxidative scission of aromatic olefins to carbonyl compounds by molecular oxygen.

A simple, and practical oxidative scission of aromatic olefins to carbonyl compounds using O2 as the sole oxidant with poly(ethylene glycol) dimethyl ether as a benign solvent has been developed. A wide range of monosubstituted, gem-disubstituted, 1,2-disubstituted, trisubstituted and tetrasubstituted aromatic olefins was successfully converted into the corresponding aldehydes and ketones in excellent yields even with gram–scale reaction. Some control experiments were also conducted to support a possible reaction pathway.

Sustainable synthesis of vinyl methyl ether from biomass-derived ethylene glycol dimethyl ether over solid base catalysts

A green and efficient route has been developed for the sustainable synthesis of high value-added vinyl methyl ether from biomass-derived ethylene glycol dimethyl ether on solid bases.

High-rate and high sulfur-loaded lithium-sulfur batteries with a polypyrrole-coated sulfur cathode on a 3D aluminum foam current collector

In this study, the high-rate performance of high sulfur-loaded cathodes have been demonstrated using a novel battery that comprises of a 3 dimensional aluminum foam (current collector), sulfur (active material), acetylene black (conductive additive), and polypyrrole (PPy) coating. Consequently, a stacked laminated cell was prepared, which comprised of two 70 × 70 mm2 PPy-sulfur/ketjen black sheets (sulfur-loading = 4.3 mg/cm2), 1 M lithium bis-(trifluoromethylsulfonyl)imide (LiTFSI) with dimethoxyethane (DME) and 1,3-dioxolane (DOL), (DME/DOL = 1/1 vol%), and three Li foils as the cathodes, electrolyte, and anodes, respectively. The 1 M LiTFSI DME/DOL electrolyte, which is suitable for high rate, is applicable because the PPy coating suppresses dissolution of polysulfide into the electrolyte. The discharge capacities were 462 mAh (1075 mAh/g sulfur) at 0.4C (267 mA) and 251 mAh (583 mAh/g-sulfur) at 3.8C (2670 mA). An enhanced conductive path was formed in the cathode by the 3D Al foam and AB, which considerably improved the high-rate performance. This demonstration is particularly significant from the viewpoint of commercializing the high-power output and high-energy–density Li-S batteries for industrial applications such as small mobile device and drone power source.

Physical and Electrolytic Properties of Dialkoxyethanes

1,2-Dimethoxyethane (DME, ethylene glycol dimethyl ether) and 1,2-diethoxyethane (DEE, ethylene glycol diethyl ether) are dialkyl ethers of ethylene glycol. DME shows a high boiling point as compared to diethyl ether and tetrahydrofuran. DME is also used as a reagent in organometallic chemistry and as a solvent in some electrolyte solutions for lithium batteries. The solubility of lithium salts in DEE is much less than that in DME. Partial fluorination of DEE can improve the solubility of lithium salts. In contrast, the polyfluorinated and perfluorinated organic solvents show very low polarity. These solvents are the so-called fluorous media and are often immiscible with organic solvents as well as water. We report the physical and electrochemical properties of fluorinated DEEs: monofluorinated, trifluorinated, and tetrafluorinated DEEs (EFEE, ETFEE, and FETFEE, respectively).The relative permittivity reflects the ease of progress of dielectric polarization. The relative permittivities of FETFEE, EFEE, and EFTEE decreased linearly with an increase in temperature. The relative permittivities of FETFEE, EFEE, and EFTEE decreased linearly with an increase in temperature. The relative permittivity of FETFEE was higher than those of ETFEE and EFEE: FETFEE > ETFEE ≈ EFEE > DEE. The viscosity is the property which opposes the relative motion of the adjacent layers of the liquid. It is regarded as the internal friction and affects electrolytic conductivity. The viscosity (η) of FETFEE was also higher than those of EFEE and ETFEE: FETFEE > EFEE > ETFEE > DEE. The kinematic viscositsiy (v) of ETFEE was as low as that of DEE above 323 K. The plots of log10(η/mPas) vs. T −1 and the plots of log10(v / 10−2 m2 s−1) vs. T −1 gave straight lines.The conductivity of an electrolyte solution is a key factor determining the internal resistance and rate performance of lithium batteries. The conductivities (κ) of electrolyte solutions in ETFEE and FETFEE increased with an increase in temperature (T). The viscosities of the fluorinated DEEs decreased rapidly with an increase in temperature and approached that of DEE at high temperatures. Interestingly, the conductivity of LiPF6 solution in FETFEE was higher than that in ETFEE: EFEE > FETFEE > ETFEE. The partial fluorination can increase the ability of the solvent molecules to form hydrogen bonds. The number of hydrogen atoms that are bound to the same terminal carbon atom as fluorine atoms are as given below: FETFEE (2), EFEE (2), ETFEE (0), and DEE (0). The attraction between FETFEE molecules can be based on nonconventional weak intermolecular hydrogen bonding (CF−H···O or C−H···F−C). The weak hydrogen-bonding system does not exchange its proton and therefore it is no more a genuine hydrogen bond; it is an electrostatic attraction between positive charge on the hydrogen and negative charge on the organic fluorine or the organic oxygen.The hydrogen bonding leads to the high acceptability of an electron-pair of a donor atom from a solute. This effect may result in the increased solvation of PF6 − ions and, consequently, in the higher degree of ionic dissociation. The fluoromethyl group (CH2F-) may serve as an anion-attracting group. In contrast, the polyfluorination can decrease the electron-pair donability of an oxygen atom of the C-O-C moiety. The trifluoromethyl group (CF3-) is a strong electron-withdrawing substituent. The anodic stability of FETFEE was higher than that of EFEE: FETFEE > ETFEE > EFEE. The finding suggests that the electron-pair donability decreases in the inverse order: FETFEE < ETFEE < EFEE. Fluorine is the most electronegative of all the elements. Most conventional measures for the electronic effect of substituents are provided as Taft constants (σ*) for substituents attached to aliphatic chains. The Taft constants of a trifluorometheyl group (CF3-: Taft σ* = 2.61, σ(calcd.) = 2.60) and a fluorometheyl group (CH2F-: Taft σ* = 1.10, σ(calcd.) = 1.17) are substantially larger than that of a metheyl group (CH3-: Taft σ* = 0, σ(calcd.) = −0.07). The value of 1.10 is comparable with a formyl group (-CHO: Taft σ* = 1.1, σ(calcd.) = 1.09).The product of conductivity and viscosity (κη) observed for FETFEE, ETFEE, and EFEE was slightly decreasing at high temperatures. The plots of log10(η/mPas) vs. T −1 gave straight lines. In contrast, the plots of log10(κ/mScm−1) vs. T −1 displayed upward curvature. The decrease in the κη and the convex curve show that the conductivities of LiPF6 solutions in FETFEE, ETFEE, and EFEE are not inversely proportional to the viscosities at elevated temperatures.

Application of Stabilized Lithium Metal Powder (SLMP®) in Silicon Anodes for Advanced Lithium-Sulfur Batteries

Silicon is a potential anode material for lithium-sulfur batteries. This future energy storage system has an essential higher energy density and significantly lower costs compared to lithium-ion batteries. However, a big problem by using silicon is the high volume expansion of 280 %. The volume expansion and contraction results in a break-up of the solid electrolyte interface (SEI). The SEI has to be reformed continuously during cycling, which leads to a continuous loss of lithium. One approach to compensate the lithium loss during cycling is the prelithiation of silicon anode with a stabilized lithium metal powder (SLMP ® ). SLMP can serve as an additional lithium source to mitigate the capacity loss during the first and the following cycles and improve the energy density significantly.Adding SLMP directly into the slurry during electrode production is problematic because it is incompatible with many conventional electrode components. Therefore the application of SLMP on the finished electrode as an additional layer is advantageous. For this purpose, the SLMP can be mixed in a solvent and applied to the electrode. After drying, the SLMP must still be activated by a pressing process, since the protective carbonate shell must be broken open. One problem here is the rapid separation of SLMP and solvent. A possible solution is the addition of a binder, like styrene-butadiene rubber (SBR).Here we present a silicon/graphene-based anode prelithiated with SLMP in the electrolyte systems 1 M LiTFSI, 0.2 M LiNO3 in dimethoxy ethane (DME) and 1,3-dioxolane (DOL). For this work, we used a commercially available Si/C composite material with a PAA binder. The silicon content of the electrode is 25 %. SLMP is loaded on the top of the electrode and activated by a pressing process. The advantage of a binder in the SLMP - solvent mixture will be shown, and also that the binder has no negative effect on the electrochemical properties. The electrodes are examined by galvanostatic cycling and show high coulomb efficiency of over 85 % in the first cycle. Also, the SLMP of the anode compensates the lithium loss over at least 300 cycles. We will show the improvements of the anode prelithiated with SLMP compared to pure Si/C anodes.

Lithium Polysulfide Sparingly Solvating Electrolyte for Practical High Energy Density Lithium Sulfur Battery

Safe and cheap rechargeable batteries with high energy density and long cycle performance are urgently required for the increasing market of portable electronic devices, electric vehicles (EV), and large-scale grid. Conventional lithium ion batteries (LIBs) based on Li-ion intercalation, which have been widely applied, could not satisfy the demand for higher energy density and greater driving range of EVs. Elemental sulfur, an inexpensive, abundantly available, and environmental-friendly material, has become one of the most promising positive electrode active materials because of its high theoretical specific capacity (1675 mAh g-1). Nevertheless, the commercialization of the rechargeable Li-S battery is still hindered by several main issues: the electronically insulating nature of sulfur and its discharge products (Li2S/Li2S2), the large volumetric expansion of 80% upon its full lithiation, the dissolution and shuttle effect of lithium polysulfide (LiPS).[1-4] To achieve the practical application of Li-S battery, high energy density and stable cycling performance both need to be focused on. However, for the traditional ether-based electrolyte of 1,3–dioxolane (DOL), and dimethoxyethane (DME) as solvent that is commonly utilized for Li-S battery, severe dissolution of sulfur species from cathode and shuttle effect of LiPS causes a loss of active material and poor cycling stability. To realize the high energy density of Li-S battery, the amounts of electrolyte in the whole battery system need to be controlled. Unfortunately, it is difficult to reduce the electrolyte/sulfur ratio (E/S [mL electrolyte/mg sulfur]) when using the conventional DOL/DME electrolyte because the electrodeposition of the LiPS was found to be significantly slower at high LiPS concentration for a given deposition substrate.[5] Therefore, development of novel electrolytes is of great importance to establishing high energy density Li-S batteries. Here, we report electrochemical performance of Li-S battery using the LiPS sparingly solvating electrolytes.[6-8] Based on these electrolytes, several advantages have been revealed. Firstly, the solubility of LiPS was greatly suppressed, and thus stable charge-discharge with high Coulombic efficiency was achieved in the Li-S batteries. Second, by utilizing pouch cell, we have achieved a high energy density (> 300 Wh kg-1) for Li-S battery under an extremely low E/S ratio of 3.0 μL mg-1. Third, gassing behavior of the Li-S battery using the DOL/DME electrolyte, which indicates high safety risk, could also be obviously depressed.To further improve the electrochemical performance of Li-S batteries based on LiPS sparingly solvating electrolytes with extremely low E/S ratios, we also explored sulfur electrode additives to improve the electrolyte wettability, various electrolyte additives to protect the lithium anode, and optimized making process for pouch cell. The detailed progress will be presented in the presentation. Acknowledgements This work was financially supported by the Advanced Low Carbon Technology Research and Development Program (ALCA) of the Japan Science and Technology Agency (JST).

The Effect of Temperature and SEI Formation on the Nucleation and Growth of Electrochemically Plated Lithium

Understanding the nucleation and growth process during electroplating of lithium metal is essential for enabling long cycle life in lithium metal batteries. The morphology of electrochemically plated lithium is strongly correlated with Coulombic efficiency and cycle life, and the nucleation and growth of lithium is dictated by the nature of the substrate, the characteristics of the solid electrolyte interphase (SEI), and temperature. However, there is a lack of knowledge about how these factors affect fundamental nucleation and growth processes, especially at temperatures other than room temperature. In this work, we investigate the nucleation, growth, and morphology evolution of lithium metal under different temperature conditions. Stainless steel and antimony metal are used as substrates to compare growth surfaces that are inert with those that form alloys with lithium. Ex situ SEM is used to explore the morphology evolution at temperatures ranging from -20 °C to 20 °C. In order to better track the particle size evolution over time, we use an electrolyte solution tailored to cause Li to deposit as spherical particles (a 1:1 (v/v) 1,3-dioxolane (DOL) and 1,2 dimethoxyethane (DME) mixture with 1M LiTFSI and 0.8M LiNO3). We find that as temperature increases, the particle size also increases. Furthermore, growth on lithiated antimony films results in larger average particle sizes than on stainless steel. Our experiments also show that the extent and nature of the initial SEI growth on the substrate plays a controlling role in determining the Li morphology and uniformity of growth, and prolonged growth of the SEI was found to increase the Coulombic efficiency during the first few cycles. These results highlight the sensitivity of Li to cycling conditions and temperature, and they indicate that careful control is necessary to attain high-efficiency cycling in Li metal batteries.

Fluorinated Alkoxyaluminates As Electrolytes for Calcium-Ion Batteries

In the field of multivalent Batteries, the reversibility of stripping and plating of the metal in question will dictate the overall performance of a battery. With recent advances in non-aqueous calcium electrolytes, it is now possible to reversibly strip and plate calcium at room temperature. Several new electrolytes were found since then, which all suffer from short cycle lives, due to the strong tendency of calcium metal surfaces to passivate. An alternative route to achieve longer cycle life is to alloy the Calcium anode. It was shown that Ca-Sn alloy anodes can help, extend the cycle life by preventing the formation of impenetrable passivisation layers. However, this comes with the cost of decreased energy density, since the alloying material is not involved in the Energy storage process. In this work we focused on a new electrolyte that can extend the cycle life of a calcium-ion battery (CIB) and still work with a pure calcium metal anode. Electrolytes based on alkoxy-aluminates in glycol ethers have shown high conductivity and electrochemical stability when used in Mg-Ion batteries. But more importantly, the metal deposits obtained are remarkably pure, even after hundreds of cycles. In this work, we present the Calcium homologue,calcium-tetra-1,1,1,3,3,3-hexaflouroisopropylo-aluminate Ca[Al(HFIP)4]2, in Dimethoxyethane (DME) as a promising candidate for calcium-ion batteries. Besides its high conductivity (8.99 mS/cm2 at 25°C ) and high anodic stability (>3V vs. Ca0/Ca2+), reversible stripping and plating could be sustained for up to 550 cycles.

Synthesis and Use of Zwitterion Bearing Sulfonyl(trifluoromethane sylfonyl)imide Anion as Additive for Polymer Electrolytes

In order to improve the electrochemical properties of poly(ethylene oxide), a well-known-solid polymer electrolyte, by adding zwitterion molecules, the synthesis of a new zwitterion (ZN) having imidazolium cation and sulfonyl(trifluoromethane sulfonyl)imide anion is investigated. The addition of different amounts of ZN to the mixture of lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) and poly(ethylene glycol)dimethyl ether (PEGDM) of 1000 g mol−1 does not significantly affect the transition temperature of PEGDM but causes a slight decrease in ionic conductivity of the electrolyte mixtures. However, even with the presence of only 0.05 mole fraction of ZN, the anodic stability of LiTFSI/PEGDM based electrolytes is improved to over 4.5 V vs. Li+/Li at 25 °C. This makes the new synthesized zwitterion a promising electrolyte’s additive for high voltage batteries.

Comprehensive approach for reducing health risks due to indoor air pollutants

Individuals living in an indoor environment are typically exposed to a greater variety of air pollutants than in an outdoor environment. Numerous sources of chemical emissions are found in the indoor environment, depending on the building materials as well as the lifestyle of the occupants. The quality of the indoor environment considerably impacts public health. Japan has established Indoor Air Quality guidelines (IAQGs) for 13 chemicals, including formaldehyde, acetaldehyde, xylene, ethylbenzene, styrene, 1,4-dichlorobenzene, and toluene. However, the pollutant types and concentrations have been inconsistent over time because of altered lifestyles and the development of novel household products and building materials. Therefore, a comprehensive approach and action plan for the overall reduction of health risks because of indoor air pollutants are required for public health protection. To determine the high-risk indoor air pollutants that should be reduced, a preliminary risk assessment using data from nationwide exposure assessments and existing hazard data was conducted. As the result, 11 indoor air pollutants: 2-ethyl-1-hexanol, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, ethyl acetate, butyl acetate, propylene glycol monomethyl ether, 3-methoxy-3-methylbutanol, diethylene glycol methyl ether, diethylene glycol ethyl ether, propylene glycol monomethyl ether acetate, and methyl isobutyl ketone were identified. Subsequently, we reviewed the hazard or toxicological data for the 13 chemicals with established IAQGs and the 11 novel chemicals without established IAQGs to update their hazard assessments. The reference values for acute and chronic effects were determined from the reviewed information. The process and result of the preliminary risk assessment and the progress of the updated hazard assessments are reported.

Fluorobenzene, A Low‐Density, Economical, and Bifunctional Hydrocarbon Cosolvent for Practical Lithium Metal Batteries

AbstractHighly concentrated electrolytes (HCEs) significantly improve the stability of lithium metal anodes, but applications are often impeded by their limitation of density, viscosity, and cost. Here, fluorobenzene (FB), an economical hydrocarbon with low density and low viscosity, is demonstrated as a bifunctional cosolvent to obtain a novel FB diluted highly concentrated electrolyte (FB‐DHCE). First, the addition of FB suppresses the decomposition of dimethoxyethane (DME) on the Li metal by strengthening the interactions of DME and FSI− around Li+. Second, FB efficiently elevates the content of LiF in the solid electrolyte interphase (SEI) based on its electrochemical reduction reaction. The unique solvation and interfacial chemistry of FB‐DHCE enable dendrite‐free deposition of lithium with high Coulombic efficiency (up to 99.3%) and prolong cycling life (over 500 cycles at 1 mA cm−2). The performance of FB‐DHCE is further demonstrated in full cells under practical conditions, including ambient to low temperature (–20 °C), high areal capacity (7.6 mAh cm−2), high current density (3 mA cm−2), limited excess Li (20 µm Li), and lean electrolyte (3 g Ah−1). Employing FB as a cosolvent not only opens a novel pathway to stabilize Li metal anodes, but also could greatly advance the development of Li metal batteries.

Release of human growth hormone from an in-situ implant modulated by poly(ethylene glycol) dimethyl ether and tris(hydroxymethyl) aminomethane

A patient-friendly delivery system to release human growth hormone (hGH) is very desirable. In situ forming implant systems (ISIs) can provide a long acting and effective protein delivery. In these systems, solvents and additives play major roles in drug release. In this study, four groups of PLGA-based ISIs containing hGH were prepared in N-methyl-2-pyrrolidone (NMP) and poly(ethylene glycol) dimethyl ether (PEG-DME) as solvents with and without tris(hydroxymethyl) aminomethane (Tris) as stabilizer. Several analyses were used to investigate the implants, which include release profile, viscosity, contact angle, gel permeation chromatography (GPC), scanning electron microscopy (SEM), hGH and IGF-1 serum measurements and histopathology. In in vitro release experiments, the hGH cumulative release from PEG-DME system was twice that from NMP system during 14 days, and hGH release was tripled in the presence of Tris. With the addition of Tris to the ISIs containing PEG-DME, the water penetration, interconnectivity of pores and inner channels, surface pores and hydrophilicity were increased. Moreover, the effect of Tris on the hGH stabilization synergized its positive effects and increased the hGH final cumulative release. Results of the ISIs containing PEG-DME and Tris injection in rabbits demonstrated a reduced tissue inflammation. Moreover, the 14-days serum levels of the hGH and IGF-1 of this system in recipient rabbits were comparable to those of the commercial daily injection samples.

Role of Solvent Rearrangement on Mg2+ Solvation Structures in Dimethoxyethane Solutions using Multimodal NMR Analysis.

One of the main impediments faced for predicting emergent properties of a multivalent electrolyte (such as conductivity and electrochemical stability) is the lack of quantitative analysis of ion-ion and ion-solvent interactions, which manifest in solvation structures and dynamics. In particular, the role of ion-solvent interactions is still unclear in cases where the strong electric field from multivalent cations can influence intramolecular rotations and conformal structural evolution (i.e., solvent rearrangement process) of low permittivity organic solvent molecules on solvation structure. Using quantitative 1H, 19F, and 17O NMR together with 19F nuclear spin relaxation and diffusion measurments, we find an unusual correlation between ion concentration and solvation structure of Mg(TFSI)2 salt in dimethoxyethane (DME) solution. The dominant solvation structure evolves from contact ion pairs (i.e., [Mg(TFSI)(DME)1-2]+) to fully solvated clusters (i.e., [Mg(DME)3]2+) as salt concentration increases or as temperature decreases. This transition is coupled to a phase separation, which we study here between 0.06 and 0.36 M. Subsequent analysis is based on an explanation of the solvent rearrangement process and the competition between solvent molecules and TFSI anions for cation coordination.

Solid Polymer Electrolytes Derived from Crosslinked Polystyrene Nanoparticles Covalently Functionalized with a Low Lattice Energy Lithium Salt Moiety

Three new crosslinked polystyrene nanoparticles covalently attached with low lattice energy lithium salt moieties were synthesized: poly(styrene lithium trifluoromethane sulphonyl imide) (PSTFSILi), poly(styrene lithium benzene sulphonyl imide) (PSPhSILi), and poly(styrene lithium sulfonyl-1,3-dithiane-1,1,3,3-tetraoxide) (PSDTTOLi). A series of solid polymer electrolytes (SPEs) were formulated by mixing these lithium salts with high molecular weight poly(ethylene oxide), poly(ethylene glycol dimethyl ether), and lithium bis(fluorosulfonyl)imide. The crosslinked nano-sized polymer salts improved film strength and decreased the glass transition temperature (Tg) of the polymer electrolyte membranes. An enhancement in both ionic conductivity and thermal stability was observed. For example, the SPE film containing PSTFSILi displayed ionic conductivity of 7.52 × 10−5 S cm−1 at room temperature and 3.0 × 10−3 S cm−1 at 70 °C, while the SPE film containing PSDTTOLi showed an even better performance of 1.54 × 10−4 S cm−1 at room temperature and 3.23 × 10−3 S cm−1 at 70 °C.

Functional Localized High-Concentration Ether-Based Electrolyte for Stabilizing High-Voltage Lithium-Metal Battery.

Localized high-concentration electrolytes have attracted much attention of researchers due to their low viscosity, low cost, and relatively higher electrochemical performance than their low-concentration counterparts. In our work, 1.5 M (mol L-1) locally concentrated ether-based electrolyte has been obtained by adding 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE) into a 4 M LiFSI concentrated dimethoxyethane (DME)-based electrolyte. The optimal ratio is determined by density functional theory (DFT) calculation and experimental combination, and finally, DH(3/5)-1.5M-LiFSI (DME/HFE = 3:5 by volume) is obtained. The electrolyte not only has relatively good physical properties such as low viscosity and high conductivity but also shows decent electrochemical performance. Li∥Cu half-cells can maintain a coulombic efficiency of no less than 99% after circulating for 250 cycles under the condition of 1 mA cm-2 current density and 1 mAh cm-2 lithium deposition for each cycle, and the stable battery polarization voltage was about 50 mV. Furthermore, 0.15 M lithium trifluoromethyl acetate (LiCO2CF3) has been added as an additive to enhance the oxidation stability. The new electrolyte DH(3/5)-1.65M-LiFC (LiFC/LiFSI + LiCO2CF3) makes Li||NCM523 batteries maintain about 83% capacity after cycling for 250 times with a 0.5 C charge current density and a 1 C discharge current density of 160 mAh g-1 when charged to 4.3 V. Furthermore, this new additive has a little negative effect on the Li||Cu half-cell performance under the same condition as before, indicating this new type of localized high-concentration DME-based electrolyte benefits both high-voltage cathode and lithium-metal anode.

Goldilocks and the three glymes: How Na+ solvation controls Na–O2 battery cycling

In this work we report a framework to understand the role of solvent-salt interactions and how they mediate the performance of sodium-air/O2 batteries. The utilization of suitable electrolyte materials remains a point of major concern within the research community, as their stability and decomposition pathways during cycling are intimately connected with capacity and cycle life. Glyme based solvents have been widely utilized in Na–O2 batteries, however, to date no clear correlation between solvent/electrolyte properties and battery performance has been given. Herein, we have examined the effect of glyme chain length (ethylene glycol dimethyl ether DME; diethylene glycol dimethyl ether, DEGDME; and tetraethylene glycol dimethyl ether, TEGME) on the cycling behaviour of Na–O2 batteries and conclude that overall cell performance is highly dependent on solvent selection, salt concentration and rate of discharge/charge. We demonstrate how solvent selection helps define cell chemistry and performance by linking salt-solvent interactions to enthalpy of dissolution - and subsequently to sodium battery electrolyte properties - through the combination of both experimental and theoretical methodologies. The approaches detailed in this study could be used to predictively prepare electrolytes for Li-air batteries, other glyme-based electrochemical systems and low temperature applications.

Optimizing Calcium Electrolytes by Solvent Manipulation for Calcium Batteries

AbstractCalcium is a highly attractive metal anode because of its high earth abundance and low reduction potential. However, the lack of calcium electrolytes for reversible calcium deposition significantly hampers the development of Ca rechargeable batteries. Herein, the calcium deposition/stripping behaviors of a calcium salt electrolyte, Ca[B(hfip)4]2 ([B(hfip)4]−=tetrakis(hexafluoroisopropyloxy)borate) were systematically studied using different working electrodes (GC, Pt, Cu, and Al) and different solvents including tetrahydrofuran (THF), dimethoxyethane (DME), and diglyme (DGM). It was found that the Ca[B(hfip)4]2/DGM electrolyte demonstrated the highest reversibility and stability in cyclic voltammetry and symmetric Ca/Ca half‐cell studies. The Ca[B(hfip)4]2/DGM electrolyte was further employed to demonstrate a 3.4 V Ca battery using a FePO4 cathode with a discharge capacity of 120 Ah/mg.