Electronic structure of lithium battery interphase compounds: comparison between inelastic x-ray scattering measurements and theory |
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Authors: | Fister Tim T Schmidt Moritz Fenter Paul Johnson Chris S Slater Michael D Chan Maria K Y Shirley Eric L |
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Institution: | Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA. fister@anl.gov |
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Abstract: | In lithium ion batteries, decomposition of the electrolyte and its associated passivation of the electrode surface occurs at low potentials, resulting in an electronically insulating, but Li-ion conducting, solid electrolyte interphase (SEI). The products of the SEI and their chemical constituents/properties play an important role in the long-term stability and performance of the battery. Reactivity and the sub-keV core binding energies of lithium, carbon, oxygen, and fluorine species in the SEI present technical challenges in the spectroscopy of these compounds. Using an alternative approach, nonresonant inelastic x-ray scattering, we examine the near-edge spectra of bulk specimens of common SEI compounds, including LiF, Li(2)CO(3), LiOH, LiOH·H(2)O, and Li(2)O. By working at hard x-ray energies, we also experimentally differentiate the s- and p-symmetry components of lithium's unoccupied states using the evolution of its K edge with momentum transfer. We find good agreement with theoretical spectra calculated using a Bethe-Salpeter approach in all cases. These results provide an analytical and diagnostic foundation for better understanding of the makeup of SEIs and the mechanism of their formation. |
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