Ethylene carbonate electrolytes

Naji, A., Ghanbaja, J., Humbert, B., Willmann, P., and Billaud, D. (1996). Electroreduction of graphite in LiC104-ethylene carbonate electrolyte. Characterization of the passivating layer by transmission electron microscopy and Fourier-transform infrared spectroscopy. J. Power Some., 63, 33—9. 

Borodin, O. Smith, G. Quantum chemistty and molecular dynamics simulation study of dimethyl carbonate ethylene carbonate electrolytes doped with IiPF6, J. Phys. Chem. B 2009,113, 1763-1776. 

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,... 

The electrolyte was a mixture of ethylene carbonate and diethyl carbonate containing 1 mol L LiPFfi. In order to attain a high-voltage charge, an aluminum substrate was used. The data in Fig. 50 were taken at the charge cutoff potential of 4.3... 

Figure 7. First- and second- cycle constant-current charge/discharge curves of graphite Timrex KS44 in LiN(S02CF3)2/ethylene carbonate/dimethyl carbonate as the electrolyte (CilT irreversible specific charge Crev =reversible specific charge) [2J.

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]. 

The interfacial properties of gel electrolytes containing ethylene carbonate immobilized in a polyacrylonitrile (PAN) matrix with a lithium (bis)trifluoromethane sulfonimide (LiTFSI) salt have been studied 1139]. SEI stability appeared to be strongly dependent on the LiTFSI concentration. A minimum value of / SE1 of about 1000 Qcm2 was obtained after 200h... 

Figure 1. Temperature variation of the conductivity for a cross-section of polymer electrolytes. PESc, poly (ethylene succinate) PEO, polyethylene oxide) PPO, polypropylene oxide) PEI, poly(ethyleneimine) MEEP, poly(methoxyethoxy-ethoxyphosphazene) aPEO, amorphous methoxy-linked PEO PAN, polyacrylonitrile PC, propylene carbonate EC, ethylene carbonate.

The preparation and properties of a novel, commercially viable Li-ion battery based on a gel electrolyte has recently been disclosed by Bellcore (USA) [124]. The technology has, to date, been licensed to six companies and full commercial production is imminent. The polymer membrane is a copolymer based on PVdF copolymerized with hexafluoropropylene (HFP). HFP helps to decrease the crystallinity of the PVdF component, enhancing its ability to absorb liquid. Optimizing the liquid absorption ability, mechanical strength, and processability requires optimized amorphous/crystalline-phase distribution. The PVdF-HFP membrane can absorb plasticizer up to 200 percent of its original volume, especially when a pore former (fumed silica) is added. The liquid electrolyte is typically a solution of LiPF6 in 2 1 ethylene carbonate dimethyl car-... 

Fig. 15.6 Cyclic voltammogram of Cu5.5SiFe4SiiT2S32 in 1 M LiBp4 electrolyte of ethylene carbonate and dimethyl 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. 

Tadic et al. studied the polymer poly-vynilidene fluoride/hexa-fluoropropylene ( PVdF/HFP ) containing lithium salt solution in Ethylene carbonate/diethylene carbonate ( EC/DEC )- In order to understand better the effect of anion size in the electrolyte, two Li salts were compared, namely LiN(CF3S02)2 (termed Liimide by the authors) and LiN(C2F5S02)2 (termed Libeti ). 

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... 

As the electrolyte, 1M solution of Lithium hexafluorophosphate in the mixture of ethylene carbonate and diethyl carbonate (1M LiPF6 EC DEC=1 1 - electrolyte LP-40 by Merck) was used. 

The electrolyte used in the lithium cell studies was typically 1,2M LiPF6 in ethylene carbonate (EC) propylene carbonate (PC) methyl ethyl carbonate (MEC) in a 3 3 4 mixture. The cells were cycled at room temperature using Maccor Series 4000 control unit in a galvanostatic mode under a constant current density of 0.1 to 1 mA/cm2. 

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). 

High-power Li-ion cells with a LiNio.8Coo.15Alo.05O2 cathode, a synthetic graphite anode, 1.2 M LiPF6 + ethylene carbonate + ethyl-methyl carbonate (EC/EMC) electrolyte, and a Celgard 2300 separator, were... 

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. 

Electrolyte solutions of various aprotic organic solvents are used in primary lithium batteries. Among the organic solvents are alkyl carbonates [PC (er = 64.4-), ethylene carbonate (EC, 89.640°c)> dimethyl carbonate (DMC, 3.1), diethyl carbonate (DEC, 2.8)], ethers [DME (7.2), tetrahydrofuran (THF, 7.4), 2-Me-THF (6.2),... 

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