J. Khanderi, J.J. Schneider / Inorganica Chimica Acta 370 (2011) 254–259
259
T, Oxygen,
solid state
T, Argon,
solid state
O
T
LiFeO2 + CO2
Fe2O3 + Li2CO3
Fe + Fe3C + Li2O/Li2CO3
Fe
Li
O
- C5H5
- DME
- COD
1
O
T, annealing
T, Argon, DMF, solution
[Fe/Li/C/O polymeric]
Li2Fe3O5 + Li5FeO4
Fe
Li
O
1
Fig. 11. Reaction scheme for the decomposition and further reactions leading to the formation LiFeO2 from compound 1.
Cordier (XRD) and Dr. Jörg Engstler (TEM), for technical assistance.
We thank the Ernst-Ruska-Zentrum, Jülich (Prof. H. Meyer, Dr. L.
Houben, Dr. A. Lysberg) for making TEM studies possible (under
Project ERC1-TUD).
4. Discussion
The solid state decomposition of the precursors 1–3 in the ab-
sence of oxygen results in the formation of iron, Fe3C, and Li2O/
Li2CO3, the latter formed reaction of Li with traces of oxygen and
CO2/H2O as indicated by XRD, IR and TG. TG/MS shows that the or-
ganic ligand sphere for 1–3 is eliminated already below 200 °C.
TEM of the product obtained at 200 °C shows particle dimensions
of 2–4 nm are embedded inside an amorphous matrix. Fe(II) and
Fe(III) is formed during the initial decomposition starting from Fe
(0) in the precursors and form the mixed iron oxide, which further
reacts with Li2CO3 resulting in formation of LiFeO2.
In the case of the solution phase decomposition, ferrites such as
Li2Fe3O5 or Li5FeO4 are formed indicating a different decomposi-
tion pathway compared to the solid state. The decomposition reac-
tions based on the spectroscopic and microscopic findings
resulting in the formation of LiFeO2 from 1, are depicted in Fig. 11.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
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5. Conclusions
Lithium containing ferrocene derivatives of the type
[(Cp)Fe(COD)Li  (L)] (L = DME, TMEDA) and [(Cp)2FeLi2  2 L]
(L = TMEDA) are suitable single source precursors for the prepara-
tion of lithium ferrites of various compositions. These organome-
tallic compounds can be decomposed in the solid state as well as
in solution to give solid state ferrite materials. The decomposition
in inert atmosphere leads to the formation of a mixture Fe, Fe3C
and Li2O/Li2CO3 as precursor material with the complete removal
of all organic ligands. These initially formed components react fur-
ther under oxidative conditions to form LiFeO2 by reaction of iron
oxide and Li2O/Li2CO3. The so formed amorphous LiFeO2 crystal-
lizes as the temperature is further increased. HRTEM of the final
product obtained at 600 °C reveals no crystalline order. In the case
of solution phase decomposition, various fragments containing
lithium and iron might react in a more complicated route leading
to the formation of other ferrites. The electrochemical test of the
a-LiFeO2 formed via the solid state decomposition route shows
an initial capacity of 13 mAh/g with a rapid decrease in capacity.
To conclude, lithium containing ferrocene derivative are promising
precursors for the synthesis of lithium ferrites.
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Our work is supported through the Deutsche Forschungsgeme-
inschaft (DFG). We acknowledge Dr. Rudolf C. Hoffmann (TG/MS),
Dr. Alexsander Issannin (XPS), Dr. Kathrin Hofmann, Dr. Gerhard