Lithium Ethylene Dicarbonate Identified as the Primary Product of Chemical and Electrochemical Reduction of EC in 1.2 M LiPF₆/EC:EMC Electrolyte

Abstract

Lithium ethylene dicarbonate ((CH2OCO2Li)2) was chemically synthesized and its Fourier transform infrared (FTIR) spectrum was obtained and compared with that of surface films formed on Ni after cyclic voltammetry (CV) in 1.2 M lithium hexafluorophosphate (LiPF6)/ethylene carbonate (EC):ethyl methyl carbonate (EMC) (3:7, w/w) electrolyte and on metallic lithium cleaved in-situ in the same electrolyte. By comparison of IR experimental spectra with that of the synthesized compound, we established that the title compound is the predominant surface species in both instances. Detailed analysis of the IR spectrum utilizing quantum chemical (Hartree-Fock) calculations indicates that intermolecular association through O...Li...O interactions is very important in this compound. It is likely that the title compound in the passivation layer has a highly associated structure, but the exact intermolecular conformation could not be established on the basis of analysis of the IR spectrum.

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

“…64 Vibrations around 1650 cm −1 , 1320 cm −1 and 1150 cm −1 reflected the presence of alkyl carbonates like (CH 2 OCOOLi) 2 . 65 Again, components in the SEI from different cycled anodes varied considerably, consistent with the XPS analysis. For example, the feature belonging to (CH 2 OCOOLi) 2 was stronger in the cycled SLC 1520T graphite anode, while both MAGE and MAGE3 graphite showed much stronger Li 2 CO 3 signals (Figure 6d).…”

Identification of Diethyl 2,5-Dioxahexane Dicarboxylate and Polyethylene Carbonate as Decomposition Products of Ethylene Carbonate Based Electrolytes by Fourier Transform Infrared Spectroscopy

“…Details of ex-situ FTIR-ATR analysis have been reported in earlier publications. 21,23,24 The Ni foil IR experiments and spectra are from a previous paper 4 .…”

“…Therefore, as an indispensable component of the electrolytes of state-of-art LIBs, EC decomposition primarily controls the electrolyte decomposition process 4 . The products are widely known to contain both organic and inorganic components such as lithium alky carbonates (e.g.…”

“…Several theoretical and experimental studies have been performed to determine the effect of Li + solvation on IR vibration spectra of electrolytes solvent and electrolyte decomposition. 4,[14][15][16][17] . Even though neither DEDOHC nor poly-EC is lithium compounds, lithium salt can be dissolved in these compounds and therefore it is essential that FTIR reference spectra include the solvation contribution.…”

Control of Surface Chemistry and Electrochemical Performance of Carbon-coated Silicon Anode Using Silane-based Self-Assembly for Rechargeable Lithium Batteries

“…For the surface characterization, we focus on ex-situ IR measurement with attenuated total reflection (ATR) geometry that is very sensitive to surface species and provides direct information on the functional groups of surface molecules. [22][23][24][25][26] Here we report a surface modification approach to stabilize surface structure and cycling performance of carbon-coated Si thin-film electrode. Surface modification by self-assembly of organoalkoxysilanes with different number of organoalkoxy group and SEI layer formation resulting from electrode/electrolyte interfacial reactions were determined using ex-situ IR spectroscopy with attenuated total reflection (ATR) geometry.…”