Lithium ethylene dicarbonate

The direct evidence of this reaction mechanism is the observation of carbonyl stretching signature at -1,650 cm" in FTIR spectrum. The decomposition products from lithium salt were also found through the XPS surface analysis, such as alkoxides or oxides, a competition reaction between solvents and salts. However, the formation of alkyl carbonate seems to be predominant when EC is the component of electrolyte because of the more reactive nature of EC toward cathodic reductions [28]. The formation of lithium alkyl carbonate was also confirmed in an independent work, where the reduction products of EC in a supporting electrolyte were hydrolyzed by DjO and then subject to NMR analysis, which identified ethylene glycol as the major products formed, as indicated by the singlet at H spectrum [29]. Therefore, Aurbach and co-workers concluded the reduction products of EC and PC, lithium ethylene dicarbonate (LEDC) and lithium propylene dicarbonate (LPDC), respectively ... 

Fig. 5.7 The H- and C-NMR of the synthesized lithium ethylene dicarbonate (LEDC, left) and lithium propylene dicarbonate (LPDC, right), and the proposed reduction of EC and PC through single-electron pathway, respectively (reproduced with permission by the American Chemical Society from [38])...

Fig. 5.8 FTIR spectra of (a) synthetic lithium ethylene dicarbonate (b) surface species on the Ni electrode after Li deposition cycling between -0.5 and +2.5 V (c) ECiLiPFg solvate (reproduced with permission by American Chemical Society from [39])...

Zhuang GV, Xu K, Yang H, low TR, Ross PN (2005) Lithium ethylene dicarbonate identified as the primary product of chemical and electrochemical reduction of EC in 1.2 M LiPFgEC EMC electrolyte. J Phys Chem B 109 17567-17573... 

Regarding other termination reactions of the radical anion 38, the differences of AG with the corresponding reactions of LF(EC)2 are around 1.0 kcal/mol, e.g. 0.3 kcal/mol less negative for the Li carbide (50) generation, 0.6 and 1.4 kcal/mol more negative for lithium ethylene dicarbonate (48) and lithium diethylene dicarbonate (49), respectively, and nearly identical for the R-0-Li compound (51). This implies that the major effect of VC does lie in the initial step of the solvent reduction. 

Figure 12 Structures showing selected parameters calculated with B3PW91/6-3IG. (12a) Lithium ethylene dicarbonate (12b, 12c) dimer (12d-e) trimer (12f) tetramer. The symbols and notations have the same meaning as those in Figure 10.

Figure 16 Simulated infrared spectra for lithium ethylene dicarbonate 12a (a), dimer 12b (b), and trimer 12e(c) with the same parameters as in Figure 14. Reproduced from [38] with permission of Amer. Chem. Soc.

Only the conformation of perpendicular adsorption (7.5, in Figure 20c) was found for LPD at the two higher levels. In the conformation 7.5 the distances from the carbonyl carbons to the nearest graphite carbon are longer, by 0.04 and 0.11 A, than those in the conformation 7.3 R 4.214, 4.000 A vs 4.172, 3.885 A at 6-3IG ), the distances R for alkyl carbons are also further increased by approximately 0.10 and 0.32 A (5.507,4.974 A vs 5.426,4.657). The results imply that the adsorption of LPD becomes looser than that of lithium ethylene dicarbonate. It is noted that the small basis set 3-2IG considerably underestimates (overestimates) R (adsorption energies before BSSE), however it qualitatively provides similar trends to 4-3IG and 6-3IG about adsorptions of the three lithium dicarbonates. In the following section the 3-21G basis set is used for the C96H24 surface. 

The selected NMR spectra of these synthesized lithium alkyl ethylene dicarbonate and lithium alkyl propylene dicarbonate are shown in Fig. 5.7. 

Borodin, O. Zhuang, G. V. Ross, R N. Xu, K., Molecular Dynamics Simulations and Experimental Study of Lithium Ion Transport in DiUthium Ethylene Dicarbonate. J. Phys. Chem. C 2013,117,7433-7444. 

Fig. 7.22 Conductivity of lithium dilithium ethylene dicarbonate (Li2EDC) > lithium methyl carbonate (LiMC) from MD simulations [91] compared to conductivity of EC/LiTESI from MD simulations [36]...

At the onset potential for reduction of about 1.5 V (Li/Li+), alkyl carbonate-based solvents, such as PC, EC, and DMC, are reduced in the presence of Li ions on nonactive electrodes to R0C02Li compounds. The most probable compounds formed in the case of PC and EC are propylene and ethylene lithium dicarbonates, respectively. The mecha-... 

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