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Open Access Publications from the University of California

Scholarly Works (6 results)

  • Article
  • Peer Reviewed
LBL Publications (2018)
Investigated the composition of the SEI layer on graphite negative electrodes under different conditions. The aim is to reveal the effect of certain electrolyte additives and/or conditioning strategies, which may lead to improved performance of Li-ion battery cells. Investigated the composition of the SEI (surface composition and depth profiling, including 3D investigation) upon initial lithiation of the graphitic anode. Investigated the changes in the SEI (surface composition and depth profiling, including 3D investigation) on 1st delithiation of the graphitic anode. The following techniques were used: ex situ and in situ NFIR and LIBS techniques.
    Cover page: Analysis of SEI film on graphitic anode material using NFIR and LIBS
    • Article
    • Peer Reviewed
    LBL Publications (2018)
    Developed an in situ method of imaging and analysis of local potential distribution in model and composite Li-ion electrodes during charge/discharge process. Used a scanning probe microscope to detect and image potential differences within the electrode and the corresponding variations of the active material local state of charge.
      Cover page: CRADA: In situ analysis of potential distribution in Li-ion Batteries
      • Article
      Lawrence Berkeley National Laboratory (2003)

      Lithium-ion cells, with graphite anodes and LiNi0.8Co0.15Al0.05O2 cathodes, were cycled for up to 1000 cycles over different ranges of SOC and temperatures. The decline in cell performance increases with the span of SOC and temperature during cycling. Capacity fade was caused by a combination of the loss of cycleable Li and degradation of the cathode. The room temperature anodes showed SEI compositions and degrees of graphite disorder that correlated with the extent of the Li consumption, which was linear in cell test time. TEM of the cathodes showed evidence of crystalline defects, though no major new phases were identified, consistent with XRD. No evidence of polymeric deposits on the cathode particles (FTIR) was detected although both Raman and TEM showed evidence of P-containing deposits from electrolyte salt degradation. Raman microscopy showed differences in relative carbon contents of the cycled cathodes, which is blamed for part of the cathode degradation.

        Cover page: Characterization of high-power lithium-ion cells-performance and diagnostic analysis
        • Article
        • Peer Reviewed
        LBL Publications (2020)
        Carbonate-based electrolytes in Li-ion batteries exhibit long range order in a frozen state, which enables their non-destructive analysis by diffraction methods. In the current study the spatial distribution of lithium and electrolyte inside the graphite anode was determined in cycled Li-ion cells using monochromatic spatially-resolved neutron diffraction measurements at 150 K. The results indicate a loss of lithium and electrolyte and their non-uniform distribution in the graphite anode in aged Li-ion cells. The observed lithium and electrolyte losses are directly correlated with two electrochemical performance degradation mechanisms, which are responsible for the cell capacity fade.
          Cover page: Inhomogeneous distribution of lithium and electrolyte in aged Li-ion cylindrical cells
          • Article
          LBL Publications (2001)
            Cover page: Failure modes in high-power lithium-ion batteries for use in hybrid electric vehicles
            • Article
            • Peer Reviewed
            LBL Publications (2017)
            Infrared-active optical phonons were studied in olivine LiFePO4 oriented single crystals by means of both rotating analyzer and rotating compensator spectroscopic ellipsometry in the spectral range between 50 and 1400 cm-1. The eigenfrequencies, oscillator strengths, and broadenings of the phonon modes were determined from fits of the anisotropic harmonic oscillator model to the data. Optical phonons in a heterosite FePO4 crystal were measured from the delithiated ab-surface of the LiFePO4 crystal and compared with the phonon modes of the latter. Good agreement was found between experimental data and the results of solid-state hybrid density functional theory calculations for the phonon modes in both LiFePO4 and FePO4.
              Cover page: Infrared-active optical phonons in LiFePO4 single crystals
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