Revealing the Formation of Dialkyl Dioxahexane Dioate Products from Ethylene Carbonate Based Electrolytes on Lithium and Potassium Surfaces

In this study, the formation of dicarbonate degradation products of ethylene carbonate-based carbonate mixtures containing dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate that were combined with lithium or potassium metal, is investigated. It is shown by NMR and GCMS that the dicarbonate products dimethyl dioxahexane dioate, ethyl methyl dioxahexane dioate and diethyl dioxahexane dioate are formed from the reactants to different extents and, in particular, the potassium surface initiates the fast formation of the corresponding dicarbonate products. Experiments with deuterated DMC suggest an intermolecular mechanism of the dicarbonate formation. In cell tests, namely potassium vs. graphite, it is shown that the electrolyte formulation with the lowest tendency to dicarbonate formation (EC/DEC) exhibited the best cell stability respectively lowest cell aging.