Tetraethylene Glycol Dimethyl Research Articles

Influence of Additives on the Electrochemical and Interfacial Properties of SiOx-Based Anode Materials for Lithium-Sulfur Batteries.

The influence of electrolyte additives on the electrochemical and interfacial properties of SiOx-based anodes for lithium-sulfur batteries (Li-S) was systematically investigated. Four different electrolyte additives, namely, lithium nitrate, vinylene carbonate (VC), vinyl ethylene carbonate, and fluoroethylene carbonate (FEC), were added to the bare electrolyte comprising 1 M LiTFSI in tetraethylene glycol dimethyl ether/1,3 dioxolane in a ratio of 1:1 (v/v). The self-extinguishing time (SET) of the liquid electrolytes was measured. The 2032-type half-cells composed of Li/SiOx/Si/C were assembled, and their charge -discharge studies were analyzed at the 0.1 C-rate. Upon cycling, the electrode materials were subjected to surface morphology and differential scanning calorimetry analyses. The interfacial properties of SiOx-based electrodes were investigated by electrochemical impedance spectroscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy studies. Among the electrolytes examined, FEC-added electrolytes offered the lowest SET and interfacial resistance values. The superior charge-discharge properties of FEC-added electrolytes were attributed to the formation of a stable solid electrolyte interface layer on the electrode surface. The surface chemistry studies revealed the formation of Li2CO3 and ROCO2Li peaks on the electrode surface.

Probing the Effect of Stoichiometric Ratio of Mg(CF3SO3)2/AlCl3 on Optimizing the Electrolyte Performance for Mg Sulfur Battery

The low cost and safety qualify Magnesium (Mg) metal batteries to be one of the utmost post-lithium batteries. Nonetheless, most Mg electrolyte suffers from conditionality and incompatibility with most the cathodes which have hindered the progress of Mg battery applications. Herein, we try to optimize a new electrolyte system based on Mg(CF3SO3)2 dissolved in co-solvent of acetonitrile (ACN) and tetra ethylene glycol dimethyl (TEGDME) via studying the effect of the stoichiometry of Mg(CF3SO3)2 and AlCl3 on the electrical and the electrochemical performance. Interestingly, it is found that the electrolytes with an optimized Mg(CF3SO3)2 /AlCl3 stoichiometric ratio(0.45/0.35) yield are much more efficient reversible deposition and stripping of Mg and lower overpotential. In addition, a dual (polymer/liquid) electrolyte system is used to avoid the direct contact between the Mg anode and the liquid electrolyte to protect the Mg metal anode from passivation and adjust the position of HOMO and LUMO levels of electrode/electrolyte interface relative to the Fermi level. Furthermore, this work uses an unconventional electrode, based silicon carbide, sulfur and barium titanate to demonstrate the performance of Mg batteries. This optimized electrolyte coupled with the unconventional cathode allows high initial specific discharge capacity. The present study offers new approaches for designing high-performance rechargeable magnesium battery.

Water scavenger as effective electrolyte additive and hybrid binder‐free organic/inorganic cathode for Mg battery applications

Magnesium (Mg) metal batteries are an exciting prospect as a post lithium battery owing to the high energy density and low cost. However, the formation of a poorly ion-conductive passivation layer on Mg electrode remains a major limiting factor impeding their practical applications. Herein, we adopt a potential approach by investigating the effect of water scavengers such as hexamethyldisilazane (HMDS) and 2,2-dimethoxypropane (DMP) on the performance of MgCl2-based electrolyte dissolve in co-solvent of acetonitrile (ACN) and tetra ethylene glycol dimethyl (TEGDME). Interestingly, it is found that by introducing HMDS and DMP, the Mg ion transference number increases and the stripping/plating overpotential significantly decreases. Furthermore, organic/inorganic cathode based V2O5, graphene nanoplatelets, p-benzoquinone and 2-Ethylhexylamine is designed. This optimized electrolyte coupled with the hybrid cathode allows reversible Mg deposition/dissolution. Mg/(V2O5/p-benzoquinone) battery assembled with this electrolyte can cycle over 35 times with a specific discharge capacity over 60 mAhg−1. This study offers new approaches for designing high-performance rechargeable magnesium batteries.

Charge-Discharge and Interfacial Properties of Ionic Liquid-Added Hybrid Electrolytes for Lithium-Sulfur Batteries.

Even though lithium–sulfur batteries possess higher theoretical capacity and energy density than conventional lithium-ion batteries, the challenging issues such as poor electronic conductivity of sulfur, dendrite formation and subsequent polysulfide shuttling, and the undesirable interfacial properties of the lithium metal anode with an electrolyte impede this system from commercialization. To circumvent the dissolution of lithium polysulfides and to improve the interfacial properties of the electrolyte with the lithium metal anode, numerous tactics have been employed. Therefore, in this work, hybrid electrolytes composed of room-temperature ionic liquids of different cations with the bis(trifluoromethanesulfonyl)imide (TFSI) anion and a nonaqueous liquid electrolyte [1 M LiTFSI in tetraethylene glycol dimethyl ether/1,3-dioxolane 1:1 (v/v)] have been prepared, and their physicoelectrochemical properties were thoroughly investigated. The lithium surface upon cycling was characterized by Raman, Fourier transform infrared, and X-ray photoelectron spectroscopy analyses. The dendrite and shuttle current measurements also indicated the formation of a stable solid electrolyte interphase and lower polysulfide shuttling between the electrodes. Among the systems examined, the hybrid electrolyte composed of 1-methyl-1-propylpyrrolidinium TFSI exhibited appreciable charge–discharge characteristics, better interfacial properties with the lithium metal anode, and increased ionic conductivity which were attributed to the enhanced ion-pair interaction that is present between the 1-methyl-1-propylpyrrolidinium cation and the TFSI anion in the electrolyte which was substantiated by Raman analysis.

Attempt to tune the dielectric and optical properties in PVA/ZnO composite using tetra ethylene glycol dimethyl ether for light emitting devices

Tuning the dielectric constant of the optical materials is of prime importance to optimize their efficiency. Polyvinyl alcohol and tetra ethylene glycol dimethyl (TEGDME) matrix hybrid nanocomposites, featuring zinc oxide embedded in the polymer were fabricated by solution casting technique. TEM images showed that the introduction of tetra ethylene glycol dimethyl ether reduces the dimensions of ZnO particles and displays good distribution of the zinc oxide nanoparticles with very little particle agglomeration, respectively. The presence of tetra ethylene glycol dimethyl ether increases the optical energy gap of the composite from 3.6 to 4 eV. The Intensity and broadening of photoemission increase with increasing the ratio of TEGDME. The I–V measurements of the fabricated Cu/(PVZO/TEGDME)/Cu cell under different sun light intensity revealed that the resistivity of the composite decreases with increasing sun light intensity and the presence of tetra ethylene glycol dimethyl ether reduces the resistivity and increases the sensitivity of the composite to sun light. The tunable dielectric constant and optical properties of these polymer composites are demonstrated by increasing the TEGDME contents in the composites, making these composites potentially useful for optimizing optical and electronic devices.

Electrochemical and Analytical Characterizations of Li-S Batteries

During the last decades more attention has been paid to developing new batteries based on the lithium-sulphur electrochemical system, having high theoretical specific energy (2600 Wh kg-1). However, lithium-sulphur batteries are still far from reaching the market place due to several limitations. Among them are: (i) the use of a Li metal anode with liquid electrolyte, (ii) the insulating character of sulphur and the ending product Li2S and (iii) the soluble polysulphide species generated during the battery operation, which diffuses throughout the separator and deposits on the Li side, resulting in a loss of active material. Despite numerous reports on the mechanism of polysulfide formation the direct information on the magnitude of polysulfide shuttle (diffusion coefficients, solubility) is still missing. Thus reliable quantification of dissolved S in the electrolyte is a necessity to investigate the role of soluble S species in the S redox reaction. This might of particular interest for theoretical help in the search for the optimized composition of the battery components. Thus within these studies we focused on the development of the new simple analytical techniques/procedures that could give such information. Firstly, the electrochemistry of elemental sulphur S8 and synthesized polysulfides (Li2S4, Li2S6 and Li2S8) has been studied for the first time in the non-aqueous electrolyte 1M LiTFSIa in 1:1 (v/v) TEGDME/Dioxolaneb and in the ionic liquid electrolytes (ILs) such as 1M LiTFSI in DEME TFSIc, 1M LiTFSI in EMIm TFSId and 1M LiTFSI in BMP TFSIe. The cyclic voltammetry of S8 in the electrolytes used and mentioned above is different to the behavior reported in some organic solvents (such as THF, DMF, DMSO, or CH3CN), with two reduction and one oxidation peaks obtained. The cyclic voltammograms (CVs) in different liquids were obtained at constant temperature (25 °C) using a PC controlled Autolab PGSTAT30 potentiostat/galvanostat and a three-electrode cell. UV_Vis spectroscopy and spectro-electrochemical studies have been carried out to help the identification of the various sulphur species formed in the solutions. The main reduction products of S8 in the electrolytes used have been identified as S6 2- and S4 2- and plausible pathways for the formation of these species are proposed. The most important results of this study will be presented in more details. This study has allowed us to understand the solid sulphur-electrolyte interaction (S solubility in electrolyte, Kinetic of dissolution). Secondly, we will present our last results using HPLC - UV Visible technique to show how we were able to determine the solubility limit of sulphur, Li2S and polysulfides in different non-aqueous electrolytes for Li-S batteries. By using high performance liquid chromatography with a UV detector, the solubility of S in the different pure solvents and in the different electrolytes mentioned above, was determined. In addition, the S content in the electrolyte recovered from a discharged Li-S battery was successfully determined by the proposed HPLC/UV method. Thus, the feasibility of the method to the online analysis for a Li-S battery is demonstrated. It’s worth to emphasize that the S was found super-saturated in the electrolyte recovered from a discharged Li-S cell. Finally, we will present the results obtained for cycling using coin cells. In order to understand the influence of dissolved sulphur on cycling properties, we were interested in the study of the influence of the nature and the amount of electrolyte on the OCP self discharge. In all cases, the cycling of batteries was done in GCPL mode. In conclusion, these results are crucial for applications since they demonstrate the important effect of the electrolyte versus sulphur ratio for the good functioning of Li/S batteries. Abbreviations a Bis(trifluoromethane)sulfonimide lithium b Tetraethylene glycol dimethyl ether/1,3-Dioxalane c N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium) d Ethyl Méthyl Imidazolium Tétra fluorosulfonyl imide e 1-Butyl-1-Methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide Keywords: Li-S battery, Electrochemistry, S8, Polysulfides, Ionic liquid, HPLC-UV, Self discharge.

Effect of Additives on the Evaporation of the Most Active Isomer of Trimedlure, the Attractant for Ceratitis capitata (Diptera: Tephritidae)1

Trimedlure (TML) is a synthetic attractant for the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). This work describes the biological activity of and the evaporation of TML from cotton wick dispensers treated with the most active of the eight isomers, TML-C, both alone and mixed with additives to facilitate delivery of this solid isomer. Field bioas say and chemical analyses were used to measure effectiveness of dispensers that had been aged as long as 10 weeks. Pure TML-C deposited as tiny crystals from an acetone solution was a highly effective and long-lasting attractant. All five additives evaluated caused an increase in the evaporation rate of TML-C but, in general, did not significantly enhance the number of flies trapped. Tetra ethylene glycol dim ethyl ether (Tet EG-DM), the least volatile of additives, yielded the smallest increase in evaporation rate of TML-G Insect catches were not significantly different in relation to TML-C evaporation rates, varying from 6 to 20 mg per day (warm weather field test) or from 3 to 10 mg per day (cool weather field test). In a laboratory test using TML enhanced in isomer C (TML- 61% C), a 5°C increase in temperature (43 versus 48°C) raised evaporation rates 1.3- to 1.7- fold. The standard TML bait currently used for C. capitata detection was significantly less effective as an attractant after 2–4 weeks of aging than was TML-C alone or with additives.