Unraveling Ethylene Carbonate-Propylene Carbonate Disparity at Electrode Interface Using Femtosecond Sum Frequency Generation Vibrational Spectroscopy
Ethylene carbonate(EC)is an im-portant electrolyte used in lithium-ion batteries due to its excellent elec-trochemical performance.However,propylene carbonate(PC)differs from EC by only one methyl sub-stituent and exhibits markedly poor properties.The EC-PC disparity is still poorly understood at the molecu-lar level.In this study,we demonstrated that femtosecond broadband sum frequency genera-tion vibrational spectroscopy(SFG-VS)with simultaneous measurement of multiple polariza-tion combinations provides a powerful probe for investigating the physicochemical processes at the electrode-electrolyte interface during the charge-discharge cycles of lithium batteries.Using monolayer graphene as the working electrode,we observed the distinct reaction out-comes of EC and PC on the electrode surface.The interfacial reaction of EC occurred only in the first charge-discharge cycle,while the interfacial reaction of PC was ongoing along with the charge-discharge cycles,which explains why EC is a better electrolyte choice than PC.This study provides direct experimental evidence in elucidating the differences in interfacial performance between EC and PC,facilitating a deeper understanding of battery interface re-actions and guiding the design of high-performance lithium-ion batteries.
Sum frequency generation vibrational spectroscopyEthylene carbonatePropy-lene carbonateSolid electrolyte interphase
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