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Materialien/Werkstoffe Vortrag: Fr., 10:00–10:20 F-V50
Combined neutron and synchrotron diffraction study of Li(Ni,Co)O2 in Liion
batteries at different charging states
Kristian Nikolowski 1 , Helmut Ehrenberg 1 , Natascha Bramnik 1 , Anatoliy
Senyshyn 1 , Markus Hölzel 1 , Carsten Baehtz 2
1 Institute for Materials Science, Darmstadt University of Technology, Petersenstr. 23,
D-64287 Darmstadt, Germany – 2 HASYLAB, Notkestr. 85, D-22607 Hamburg, Germany
LiCoO2 with a cation-ordered rocksalt superstructure is the standard cathode material
in Li-ion batteries for high-energy applications. The partial replacement of Co
by other 3d-transitional metals is an intensively studied approach to enhance thermal
stability of this cathode material, to reduce costs or to improve cycle stability. The
effect of annealing temperature on the structure and the electrochemical properties of
Ni-substituted material was previously reported [1]. In addition, a model for the conditioning
of Li(Ni,Co)O2 during the first charge-discharge cycles was proposed based
on in situ synchrotron diffraction at beamline B2, HASYLAB, Germany [2]. The advantages
of this synchrotron study, in situinvestigation and high angular resolution,
are now combined with the benefits of neutron diffraction: Li-ions become visible, the
occupation factor of the oxygen site can be refined and Ni versus Co can be distinguished.
In a first step two series of Li1−x(Ni0.8Co0.2)O2 samples are studied by ex
situ neutron powder diffraction at SPODI, FRM II. One sample has a low degree of
cation disorder and shows good electrochemical properties, another sample has a high
degree of disorder and a poor Li-extraction and Li-reinsertion behaviour. Both samples
are studied as-prepared, charged to x = 0.5 and after one complete charge-discharge
cycle. These experiments contribute to establish in situ neutron diffraction on Li-ion
batteries as a complementary tool to our in situ synchrotron diffraction studies [3].
[1] T. Gross, Th. Buhrmester, K. G. Bramnik, N. N. Bramnik, K. Nikolowski, C. Baehtz,
H. Ehrenberg, H. Fuess, Structure-intercalation relationships in LiNiyCo1−yO2,
Solid State Ionics 176 (2005) 1193-1199.
[2] H. Ehrenberg, K. Nikolowski, N. Bramnik, C. Baehtz, T. Buhrmester, T. Gross,
Conditioning of Li(Ni,Co)O2 cathode materials for rechargeable batteries during the
first charge-discharge cycles, Adv. Eng. Mater. 7 (2005) 932-935.
[3] K. Nikolowski, C. Baehtz, N. N. Bramnik, H. Ehrenberg, A Swagelok-type in situ
cell for battery investigations using synchrotron radiation, J. Appl. Cryst. 38 (2005)
851-853.