Vinylene carbonate reduction potential

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 acidity of the C2 proton (indicated in the scheme above) is estimated as pKa = 24, and this corresponds to a reduction potential of 1.5 V vs Li Li°. The methylation of the C2 proton increases the reduction potential by 300 mV however, this is still not sufficiently negative for lithium battery applications and thus such ILs require the use of additives such as vinylene carbonate (VC), which form a stable solid-electrolyte interphase (SEI) layer, in order to be viable.f " ... 

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