Lithium propylene 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])...

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

Figure 18 Comparisons of the simulated spectra between the lithium vinylene dicarbonate trimer Ij(lla), lithium divinylene dicarbonate trimer 2f(llb), lithium ethylene dicarbonate trimer 3f(llc) and lithium propylene dicaibonate 4e(lld). Reproduced from [38] with permission of Amer. Chem. Soc.

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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