Electronic structure of lithium battery interphase compounds: Comparison between inelastic x-ray scattering measurements and theory

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.

Soft X-Ray Irradiation Effects of Li2O2, Li2CO3 and Li2O Revealed by Absorption Spectroscopy

“…In general, the excitonic effect would create sharp absorption features at lower energy and reduce the intensity at higher energy [47], as especially shown by the sharp features denoted a, b (red) in Li 2 O and c-g (blue) in Li 2 O 2 in Fig. 2 [34], [46].…”

Carbon-coated nanoclustered LiMn0.71Fe0.29PO4 cathode for lithium-ion batteries

“…8a and d) and LiF (Fig. 8b and e) are typical components of the SEI on electrodes [37]. The existence of MnF 2 (Fig.…”

Quantitative first-principles calculations of valence and core excitation spectra of solidC60

“…Electron self-energy effects on real parts of band energies were determined following Fister et al, 44 but with a 10% enhancement of band-energy separations near the Fermi level. Damping was estimated using the multipole-pole self-energy treatment of Kas et al 45 using the experimental small- q (optical) loss function, i.e., −Im[1/ ε ( q → 0, ω )], from Yagi et al 19 The extended x-ray absorption fine structure (EXAFS) Debye-Waller (DW) factor (using Hartree atomic units with e = 1, ħ = 1, m e = 1) is $exp(-2k^2{\sigma }_i^2)$, where k = [2( E − E 0 )] 1/2 is the EXAFS wave number defined relative to the edge energy E 0 , and ${\sigma }_i^2$ is the mean square relative displacement for scattering path i .…”

“…44 For damping of electron-hole pair states, we averaged over all pair states with band-energy differences within 0.05 eV-wide bins. This defined an effective electron-hole-pair damping function, ${\mathrm{normal\sum }}_{\text{eh}}^{″}(E)$, which could be interpolated with respect to energy.…”