Adsorption
and Reaction Branching of Molecular Carbonates on Lithiated C(0001)
Substrates
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Abstract
The
desorption and interactions of ethylene carbonate (EC) and dimethyl
carbonate (DMC) with clean and lithiated graphite substrates were
measured by temperature-programmed desorption (TPD) and reaction (TPR)
methods under UHV conditions. Both EC and DMC interact weakly with
the clean C(0001) surface with adsorption energies of 0.60 ±
0.06 and 0.64 ± 0.05 eV, respectively. Addition of Li<sup>+</sup> to the C(0001) substrate significantly increases the binding energies
of molecular carbonates, and the range of measured values is indicative
of EC solvation of lithium ions. EC undergoes complete decomposition
on metallic Li films. Organolithium products were quantified by TPR,
and the amount of lithium carbonate product was determined by detailed
mass balance analysis. Decomposition of 1.5 L of EC resulted in the
formation of 0.64 ± 0.12 L of lithium ethylene dicarbonate, 0.40
± 0.05 L of lithium ethylene glycolate, and 0.5 ± 0.2 L
of lithium carbonate. The branching ratio at the immediate EC–metallic
lithium interface was determined as 70.% organolithium products vs
30% inorganic lithium product