In this study, we prepared single-walled carbon nanotube
electrodes
for lithium–air batteries (LABs) to investigate the structural
changes of the electrodes during the discharge–charge cycle
coupled with the precipitation and decomposition of Li oxide. Wide-angle
X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) were
used for the structural analysis. A new test cell was designed and
fabricated to perform these measurements under operando conditions. From the results of the WAXS measurements during discharge
tests, diffraction peaks indicating crystalline oxides and a broad
peak indicating amorphous components were observed. The intensities
of these peaks increased rapidly in the later stages of the discharge.
Moreover, the WAXS measurements showed that the peak of the amorphous
component preferentially disappears during the charging process. Furthermore,
the nanoscale structural changes associated with the precipitation
and decomposition of Li oxide were analyzed using SAXS. The results
suggest that the electrode expansion caused electrolyte depletion
in the electrode. The post-test electrode thickness was also analyzed,
and the results support interpreting the data obtained from WAXS and
SAXS. We think that the structural analysis approach and the pore
formation discovered in this study will enable LABs to be used more
effectively in the future.