V. Focused Fundamental Research - EERE - U.S. Department of ...

V.F.2 Novel In Situ Diagnostics Tools for Li-ion Battery Electrodes (LBNL)
Cabana, Kostecki – LBNL
discharge/charge illustrate the massive changes in the collapse and the formation of nanoparticles. During the
morphology that occur when Li reacts with NiO. The experiment, spectroscopic information was obtained to
impact and changes of morphology are shown in Figure V - track the distribution of metallic Ni and NiO during the
220. The conversion reaction leads to a drastic volume reaction.
expansion which swells the particle and leads to its
Figure V - 220: Morphology changes in a NiO particle during electrochemical cycling.
XRS data at the Li and C K edges was collected for a
sample of highly oriented pyrolytic graphite (HOPG)
before and after lithiation. The results at the C K edge
(Figure V - 221) show a remarkable decrease in the * signal,
which is related to the filling of unoccupied bands above
the Fermi level. This filling is at the origin of the metallic
character of lithiated graphite. A shift in the * signal
toward lower energies was also observed, which is related
to a stiffening of the C-C bonds upon lithiation. The Li K
edge data show that Li is far from being completely
ionized within the structure of the material, contrary to
previous studies.
Figure V - 221: XRS data at the C K edge for pristine and lithiated HOPG.
A setup for in operando XRS was also designed and
successfully tested in the laboratory. Preliminary
experiments show that the setup is very well suited for the
collection of XRS simultaneous to the lithiation of
graphite. Results are expected during FY2012.
Conclusions and Future Directions
Chemical maps of the species involved in the Li
deintercalation mechanism in LiFePO 4 were produced in
both 2D and 3D for particles of different sizes. The
distribution of phases within a crystal was uncovered. In
parallel, a setup designed for in operando data collection
was built and successfully used at the beamline. Further
experiments will leverage this new capability to follow the
chemical phase transformations front during
electrochemical reactions in different battery electrodes.
Attempts will be made to collect data in both 2D and 3D.
Data at the Li and C K edge were collected for
samples of graphite at different lithiation states. The data
reveal the complex bonding nature of the material, with a
covalent Li-C interaction leading to a material with
metallic character. In operando measurements have also
been demonstrated. Further work during FY2012 will be
directed at the full leveraging of this capability to follow
the chemical interactions between Li and the graphite
during intercalation reactions.
Energy Storage R &D 668 FY 2011 Annual Progress Report