Solvents ethyl-methyl carbonate

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]. 

A typical lithium-ion cell consists of a positive electrode composed of a thin layer of powdered metal oxide (e.g., LiCo02) mounted on aluminum foil and a negative electrode formed from a thin layer of powdered graphite, or certain other carbons, mounted on a copper foil. The two electrodes are separated by a porous plastic film soaked typically in LiPFe dissolved in a mixture of organic solvents such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), or diethyl carbonate (DEC). In the charge/ discharge process, lithium ions are inserted or extracted from the interstitial space between atomic layers within the active materials. 

Most of the liquid electrolytes used in the commercial lithium-ion cells are the nonaqueous solutions, in which roughly 1 mol (tar (= M) of lithium hexafluoro-phosphate (LiPF ) salt is dissolved in the mixture of carbonate solvents selected from cyclic carbonates - ethylene carbonate (EC), and propylene carbonate (PC) and linear carbonates - dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) -, whose chemical structures are displayed in Fig. 4.2. Recently, another type of liquid electrolyte based on 1.5 M LiBFyy-butyrolactone (GBL) + EC came onto the market for the laminated thin Uthium-ion ceUs with an excellent safety performance. Many other solvents and Uthium salts have limited appUcations, although much effort has been made to develop new materials. Into the above baseline electrolyte solutions, a small amount of the additives are dissolved, which are so-called functional electrolytes. ... 

Most liquid electrolytes used in commercial lithium-ion cells are nonaqueous solutions, in which roughly 1 mol dm of lithium hexafluorophosphate (LiPF ) salt is dissolved in a mixture of carbonate solvents selected from cyclic carbonates, e.g., ethylene carbonate (EC) and propylene carbonate (PC), and linear carbonates, e.g., dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), as listed in Table 2.1 [1]. 

Among the carbonate solvents used in practical lithium batteries, linear carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are well-known good co-solvents (thinner) for EC and PC. The direct fluorination of DMC gave fluorinated derivatives such as mono-fluorinated one, fluo-romethyl methyl carbonate (FDMC), two di-fluorinated ones (bis(fluoromelhyl) carbonate, DFDMC, and difluormethyl methyl carbonate, gem-DFDMC), and tri-fluorinated ones (difluoromethyl fluoromethyl carbonate, TFDMC) as shown in Scheme 2.6 [33]. Three kinds of partially fluorinated DMCs except gm-DFDMC were obtained by fractional distillation of the fluorinated sample. 

Ding, M. S. Xu, K. Zhang, S. S. Amine, K. Henriksen, G. L. low, T. R., Change of conductivity with salt content, solvent composition, and temperature for electrolytes of LiPp6 in ethylene carbonate-ethyl methyl carbonate, J. Electrochem. Soc. 2001,148, A1196-A1204. 

Organic solvents such as propylene carbonate, ethylene carbonate, ethyl methyl carbonate, and so on. 

The of P= Na in mixtures of A=EG and B=MeCN was interpreted in terms of the stepwise replacement of B in 1B + by A, taking into account the nonideality of the Ah-B system. Quantitative evidence for the preferential solvation of sodium ions by ethylene glycol was obtained by Chuang et al. [52]. The 5. , of of the carbonyl group in 1M solutions of LiPF in binary solvent mixtures involving esters and amides was interpreted in terms of preferential coordination of the solvents to Li with a constant total coordination number of 4. In isomolar mixtures of A=methyl propionate and B = ethyl methyl carbonate Xg = 0.39, of A=MA -dimeth-ylacetamide and B=propylene carbonate Xg =0.40, and of A=methyl propionate and B = ethyl propionate Xg = 0.43 according to Matsubara et al. [53]. In all these cases Xg < 0.50, and hence it is solvent A that preferentially solvates the ion. 

A halogenated cydic carbonate is used as an additive which is suitably added to a base solvent comprising a mixture of a cyclic carbonate and a chain or linear carbonate. Preferably the base cyclic carbonate is ethylene carbonate and the linear carbonate is ethyl methyl carbonate or diethyl carbonate (47). Some carbonate compounds are shown in Figure 2.11. 

LSV and CV measurements indicated that methylene methanedisulfonate has a lower oxidation potential in the mixed solvents of ethylene carbonate and ethyl methyl carbonate. Further, it participates in the formation process of the CEl film. 

All Li-ion cells employ nonaqueous electrolytes comprising LiPF, (or other lithium-containing salts) dissolved in solvent mixtures of organic liquids such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), or ethyl methyl carbonate (EMC). Numerous options for the choice of salts and/or solvents in such batteries are known to exist in the market place. Additionally, additives are used to modify reactivity of the anode as well as to reduce flammability of the electrolyte. 

Great efforts have been made in electrolyte development to achieve desirable hthium-ion conductivity, dielectric constant, viscosity, and thermal stabihty. The solvent systems include single solvent [35, 36] and cosolvent [37-44]. A mixture of ethylene carbonate (EC) and dimethyl carbonate/ethyl methyl carbonate (DMC/EMC) has been widely adopted by researchers and manufacturers [45-48]. liPFe is the preferred salt due to its overall performance [49]. An overview of electrolyte development is provided by Ahmad [49], and electrolyte processing has also been discussed elsewhere [50]. In addition, the introduction of hthium-ion... 

Table 11.1 Organic carbonates and esters as electrolyte solvents [1] with EC ethylene carbonate, PC propylene carbonate, BC butylene carbonate, yBC y butylene carbonate, yVC y-valerolactone, NMO Af-methyl-2-oxazolidinone, DMC dimethyl carbonate, DEC diethyl carbonate, EMC ethyl methyl carbonate, EA ethyl acetate, MB methyl butyrate, EB ethyl butyrate...

Another use of 1-butene is in the production of solvents containing four carbons such as secondary butyl alcohol and methyl ethyl ketone (MEK). Secondary butyl alcohol is produced by reacting 1-butene with sulfuric acid and then hydrolysis ... 

Suitable inert solvents include methyl ethyl ketone, benzene, ethylbenzene and toluene. Suitable initiators include peresters and peroxycarbonates such as ferf-butyl perbenzoate, ferf-butyl peroxy isopropyl carbonate, fcrf-butyl peroctoate, tert-butyl peroxy isonon-... 

Atkins et al. [130] reported in 1977 that irradiation of mixtures of benzene and methyl acrylate or methyl methacrylate, both acceptors, yields mixtures of endo and exo adducts. A subsequent report from the same groups [120] describes the results of the irradiations of benzene in the presence of ethyl vinyl ether, //-butyl vinyl ether, 2,3-dihydropyran, and 1,4-dioxene. In all these cases, the major products were exo-ortho photocycloadducts. The orientations of these vinyl ethers with respect to benzene, in their loose ground-state associations, were inferred from NMR spectra. For ethyl vinyl ether, n-butyl vinyl ether, 2,3-dihydropyran, and 1,4-dioxene, the vinyl proton resonances were either unaffected by a solvent change from carbon tetrachloride to hexadeuterobenzene or appeared 4-10 Flz downfield, whereas the methyl and/or methylene signals all moved up-field by 10-25 Hz. This implies an endo arrangement of the molecules in the ground state. Thus, the ortho photocycloadducts of vinyl ethers with benzene show exo stereochemistry, even when the ground-state orientation is endo. 

Carbonylation of propargyl carbonates bearing an amino group yields lactams. The a-vinylidene /1-lactams 82 are prepared by the carbonylation of 4-benzylamino-2-alkynyl methyl carbonates 81 [20], The best results are obtained by using the cyclic phosphite (4-ethyl-2,6,7-trioxa-l-phosphabicyclo[2,2,2]octane) (83). The lactam formation is carried out in THF or MeCN as solvents at 50 °C under 1-10 atm of CO. 

In subsequent steps, DAS is treated in acidic aqueous solution at 0-5 °C with cyanuric chloride dissolved in ethyl methyl ketone. The remaining chlorine atoms are then replaced by aliphatic, cycloaliphatic, or aromatic amines at 15-35 °C and then at ca. 60 °C. The addition of electrolytes (e.g., sodium carbonate, sodium hydroxide) or water-soluble aprotic solvents at 90 to 100 °C or above leads to the desired 3 crystal modification, which is nearly colorless. 

---