Chloroethylene 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]. 

Dichloroethyl chloroformate is a known product made by classicai chlorination of vinyl chloroformate with CI2. We have developed a new, easily practicable route by treatment of 4-chloroethylene carbonate with PCI5 at 110°C which gives a mixture of the desired chloroformate and the dichloro isomer in a 95 5 ratio as depicted in scheme 96. Careful fractional distillation afforded the 1,2-dichloroethyl chloroformate in 65 % pure yield (Ref. 125). 

The starting material, the 4-chloroethylene carbonate was prepared by standard photo-chlorination of the cheap ethylene carbonate as described in the literature. 

When ethylene carbonate is monochlorinated, the chloroethylene carbonate thus obtained is the starting material for the synthesis of vinylene carbonate which is used in radical polymerization to yield high-molecular weight polymers and copolymers or in Diels-Alder cycloadditions [Scheme 174 ] (Ref. 227). 

While studying the catalyzed decomposition of tetra-chloroethylene carbonate (V) by onium salts, we observed the formation of a little trichloroacetyl chloride. Since (V) present three reactive electrophilic centers the carbonyl group and the two carbon both linked with two chlorine atoms, it can be attacked following two different pathways as diagrammed in scheme 178. 

It is easy to know from molecular orbital calculations that the introduction of halogen atoms on cyclic carbonates make them more reducible. Chloroethylene carbonate (CIEC) was reduced at about 1.8 V vs. LP/Li and produced the passivation film accompanied by CO evolution. However, LiCl produced by its reductive cleavage was postulated to become an internal chemical shuttle, which resulted in... 

Ethylene carbonate (EC) and propylene carbonate (PC) have favorable physical and electrochemical properties such as high relative permittivity, high donicity, and relatively wide potential window. The direct fluorination of EC was successfully carried out to provide 4-fluoro-l,3-dioxolan-2-one (fluoroethylene carbonate, FEC) as shown in Scheme 2.3 [20], The fluorination of EC was strongly dependent on a choice of a reaction medium and no solvent was preferred from the viewpoint of conversion. FEC was further fluorinated to give three di-fluorinated derivatives. On the other hand, FEC was also prepared from 4-chloroethylene carbonate by exchange with KF [21], FEC was tested as an electrolyte additive for rechargeable lithium cells [21, 22] and is now practically used [23, 24],... 

In 1999 Winter et al. from the University of Munster reported the results of analyzing SEI formed by chloroethylene carbonate (4) [89], In addition, in 1999, Inaba et al. from Kyoto University and in 2002 Arai et al. from Hitachi Limited reported that trifluoromethyl ethylene carbonate (61) forms SEI [90, 91]. 

Winter, M. Imhof, R. Joho, E Novak, R, FXIR and DBMS investigations on the electroreduction of chloroethylene carbonate-based electrolyte solutions for lithium-ion cells, J. Power Sources., 1999, 81-82, 818-823. 

These include chloroethylene carbonate (Cl-EC), vinylene carbonate (VC), ethylene sulfite (ES), propylene sulfite (PS), fluoroethylene sulfite (EEC), a-bromo-y-butyrolactone, methyl chloroformate, f-butylene carbonate (f-BC), and 12-crown (12-C-4). In addition to these additives, co-solvents, such as dimethylsulfoxide (DMSO), diethoxymethane (DEM), dimethoxymethane (DMM), and diethoxyethane (DEE) are also effective for stable SEI formation in PC-based solutions. The molecular structures of these additives and co-solvents are summarized in Figure 13. It seems that all these additives give stable SEI layers on graphite surface ... 

Many efforts have been dedicated to find proper additives to PC-based solutions that would enable practical applications of PC. Some successes have been reported, including the addition of chloroethylene carbonate (CEC), other... 

PC is also a very useful solvent of LIBs because of its superior ionic conductivity over a wide temperature range. However, despite the close structural similarity between EC and PC, PC cannot form as effective SEI films as EC does, for LIBs that employ graphite as negative electrodes. " To enable to use PC in these batteries, there have been a lot of efforts focusing on the identification of proper additives and/or co-solvents for PC-based electrolytes, which would help to generate an efficient SEI layer. The typical liquid additives include chloroethylene carbonate (CEC), other halogen-substituted carbonates, a variety of unsaturated carbonates such as vinylpropylene carbonate and vinylene carbonate, and ethylene/propylene sulfite (ES/PS). The most common co-solvents are DMC, DEC, EMC, y-butyrolactone (y-BL), dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), dimethyl amide (DMA), 1,2-dimethoxy-ethane (DME) and 1,2-dimethoxy-methane (DMM). To explore the role of these additives and co-solvents, it is necessary to understand their structures and some properties that may affect the SEI formation on graphite anodes. 

Note 1,2-BC 1,2-dunethylethylene carbonate 1,3-DOL 1 -dioxolane AC acetonitrile A.N. acceptor number BC butylene carbonate BEC butyl ethyl carbonate BMC butyl methyl carbonate CF3-EC trifluoromethyl ethylene carbonate QEC chloroethylene carbonate DBC dibutyl carbonate DEC diethyl carbonate DEE 1,2-diethoxyethane DGM diethyleneglycol dimethyl ether DIPC di-isopropyl carbonate DMC dimethyl carbonate DME 1,2-dimethoxyethane DMSO dimethyl sulfoxide D.N. donor number DPC di-n-propyl carbonate EC ethylene carbonate EIPC ethyl isopropyl carbonate EMC ethyl methyl carbonate EPC ethyl propyl carbonate MeTHF 2-methyl tetrahydrofuran MIPC methyl isopropyl carbonate MFC methyl propyl carbonate PC propylene carbonate TEGM tetraethylene glycol dimethyl ether TGM triethylene glycol dimethyl ether TFIF tetrahydrofuran. 

Shu ZX, McMillan RS, Murray JJ, Davidson U (1996) Use of chloroethylene carbonate as an electrolyte solvent for a graphite anode in a lithium-ion battery. J Electrochem Soc 143 2230-2235... 

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