Solvents ethylene carbonate

An inverse decreasing relationship was found between the hydroxyl value and the reaction time for the liquefaction system. Figure 5 shows the hydroxyl value decreased steadily from h 0 to h 1.5 and then increased slightly until the end of the liquefaction (h 3). Such decrease in hydroxyl number resulted from dehydration and thermal oxidative degradation of the liquefaction solvent (ethylene carbonate). Yao et al. [7] also reported that alcohol-D-glycosides were produced by the liquefaction between polysaccharides and ethylene glycol under a temperature of 150 °C and catalyst (sulfuric acid) concentration of 3% as used in their... 

Fig. 5 Changes in hydroxyl value in the atmospheric pressure liquefaction of DDG. [Liquefaction solvent (ethylene carbonate)/ DDG ratio (g/g) 4 catalyst content 3% liquefaction temperature 160 °C]. Error bars represent standard deviations calculated from the data obtained from three replicated experiments...

Organic carbonates and fman derivatives are specialty oxygenated solvents. Ethylene carbonate and propylene carbonate are cyclic esters with good solvency, veiy slow evaporation and very low odor. Tetrahydrofuran, fiufiuyl alcohol and tetrahydrofurfiuyl alcohol are cyclic ethers with... 

Much analytical study has been required to estabHsh the materials for use as solvents and solutes in lithium batteries. References 26 and 27 may be consulted for discussions of electrolytes. Among the best organic solvents are cycHc esters, such as propylene carbonate [108-32-7] (PC), C H O, ethylene carbonate [96-49-1] (EC), C H O, and butyrolactone [96-48-0] and ethers, such as dimethoxyethane [110-71-4] (DME), C H q02, the glymes,... 

Other Derivatives. Ethylene carbonate, made from the reaction of ethylene oxide and carbon dioxide, is used as a solvent. Acrylonitrile (qv) can be made from ethylene oxide via ethylene cyanohydrin however, this route has been entirely supplanted by more economic processes. Urethane intermediates can be produced using both ethylene oxide and propylene oxide in their stmctures (281) (see Urethane polymers). 

Figure 61 shows the relationship between the discharge capacity, the initial efficiency, and the L of some soft carbon materials when ethylene carbonate was used as a solvent. Figure 62 shows the re-... 

Several solvents other than ethers have also been reported to be superior solvents for secondary lithium batteries. Ethylene carbonate showed good cycling characteristics [107, 108]. 

Numerous research activities have focused on the improvement of the protective films and the suppression of solvent cointercalation. Beside ethylene carbonate, significant improvements have been achieved with other film-forming electrolyte components such as C02 [156, 169-177], N20 [170, 177], S02 [155, 169, 177-179], S/ [170, 177, 180, 181], ethyl propyl carbonate [182], ethyl methyl carbonate [183, 184], and other asymmetric alkyl methyl carbonates [185], vinylpropylene carbonate [186], ethylene sulfite [187], S,S-dialkyl dithiocarbonates [188], vinylene carbonate [189], and chloroethylene carbonate [190-194] (which evolves C02 during reduction [195]). In many cases the suppression of solvent co-intercalation is due to the fact that the electrolyte components form effective SEI films already at potential which are positive relative to the potentials of solvent co-intercalation. An excess of DMC or DEC in the electrolyte inhibits PC co-intercalation into graphite, too [183]. 

Among many polar aprotic solvents, including ethers, BL, PC, and ethylene carbonate (EC), methyl formate (MF) seems to be the most reactive towards lithium. It is reduced to lithium formate as a major product which precipitates on the lithium surface and passivates it [24], The presence of trace amounts of the two expected contaminants, water and methanol, in MF solutions does not affect the surface chemistry. C02 in MF causes the formation of a passive film containing both lithium formate and lithium carbonate. 

Fignre 27.3 shows a typical spectroelectrochemical cell for in sitn XRD on battery electrode materials. The interior of the cell has a construction similar to a coin cell. It consists of a thin Al203-coated LiCo02 cathode on an aluminum foil current collector, a lithium foil anode, a microporous polypropylene separator, and a nonaqueous electrolyte (IMLiPFg in a 1 1 ethylene carbonate/dimethylcarbonate solvent). The cell had Mylar windows, an aluminum housing, and was hermetically sealed in a glove box. 

Currently, graphite-based lithium ion batteries use mixed solvent electrolytes containing highly viscous ethylene carbonate (EC) and low viscosity dilutants such as dimethyl carbonate (DMC) or diethyl carbonate (DEC) as main solvents. EC is indispensable because of its excellent filming characteristics. DMC and/or DEC are required to get the low temperature... 

In the case of solutions based on a solvent such as propylene carbonate (PC), the failure of graphite electrodes is attributed by some researches to the exfoliation of the graphite particles due to cointercalation of PC molecules with the Li ions.14,22 The difference between ethylene carbonate (EC) and PC in this respect may, according to this approach, be attributed to the higher ability of PC molecules to solvate Li ions.23 Hence, cointercalation of PC molecules takes place because their desolvation from Li ions, which migrate from solution phase to the intercalation sites in the graphite,... 

The electrode active masses were prepared by mixing the active material with 10 wt.% of polyvynilidene fluoride slurred in 1-methyl-pyrrolidone solvent. The actual mass was then pasted onto one side of precleaned Co foil, dried for 4 h at 100°C, pressed and the disks of 15,6 mm diameter were cut and placed into the cell s coins. Large excess of Li metal (foil) was used as a counter electrode. 1M LiPF6 solution in mixture of ethylene carbonate (50 vol.%) and methyl carbonate was used as an electrolyte (Merck product LP30). 

As a polar solvent for the catalyst ethylene carbonate (EC), propylene carbonate (PC) and acetonitrile were used. Tricyclohexylphosphine, triphenyl-phosphine and the monosulfonated triphenylphosphine (TPPMS) were investigated as ligands with Pd(acac)2 as the precursor. Cyclohexane, dodecane, p-xylene and alcohols (1-octanol, 2-octanol and 1-dodecanol) were tested as non-polar solvents for the product. To determine the distribution of the product and of the catalyst, the palladium precursor and the hgand were dissolved in the polar solvent and twice as much of the non-polar solvent was added. After the addition of 5-lactone, the amounts of the product in both phases was determined by gas chromatography. The product is not soluble in cyclohexane and dodecane, more than 99% of it can be found in the polar catalyst phase. With the alcohols 1-octanol, 2-octanol and dodecanol about 50 to 60% of the 5-lactone are located in the non-polar phase. With p-xylene biphasic systems can only be achieved when EC is used as the polar solvent and even in this solvent system one homogeneous phase is formed at a temperature higher than 70 °C. In a 1 1 mixture of EC and p-xylene about 50 to 60% of the product is contained in the polar phase. 

For this reason pyrrolidones were tested as semi-polar solvents in further experiments [25] and ethylene carbonate (EC) and butylene carbonate (BC) were examined as the polar catalyst phase instead of PC. 

The chemical structure of the electrolyte solvents critically influences the nature of the protective film, and ethylene carbonate was found to be an essential component of the solvents that protects the highly crystalline structure of graphite. 

---