Ion yields and velocity map imaging of electron attachment-induced fragmentation of linear dialkyl carbonates: exploring dissociation patterns and mechanisms

Fragmentation patterns of dissociative electron attachment (DEA) to dimethyl carbonate (DMC) and diethyl carbonate (DEC) were investigated in the 2–12 eV energy range. Four anion fragments with mass-to-charge ratios (m/z) of 15, 16, 31, and 45 were found from DEA to DMC, and five fragments with m/z 15, 16, 43, 45, and 89 were found from DEC. Their ion yields and several momentum images of dissociated anions, particularly for dissociated m/z 16 anions, were reported using velocity map imaging (VMI) spectroscopy. The m/z 43, 45, and 89 fragments were stabilized by significant charge delocalization, which is followed by electron attachment facilitated by the relatively high electron affinities of these anion. All of the fragments observed had relatively low appearance energies (3 eV) in their yields despite the fact that several fragments require multi-step dissociation processes with hydrogen shifts. We also performed density functional theory (DFT) calculations for potential dissociation channels of each fragment and compared their calculated energy threshold with their appearance energies observed in the ion yields. The difference in DEA-induced ionic products between DMC and DEC provides insight into which of these molecules degrade more extensively in lithium-ion batteries and offers valuable implications for both fundamental understanding and industrial applications.