The role of in situ generated nano-sized metal particles on the coulombic efficiency of MGeO3 (M = Cu, Fe, and Co) electrodes

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Kim, Chang H.; Jung, Yoon S.; Lee, Kyu T.; Ku, Jun H.; Oh, Seung M.

Issue Date
Electrochim. Acta 54 (2009) 4371
Lithium ion batteriesAnodeMetal oxide electrodesNano-sized metal particlesCoulombic efficiency
To improve the coulombic efficiency of GeO2 electrode, a Cu-containing ternary metal oxide (CuGeO3)
was prepared and the electrochemical behavior of Cu componentwas studied. The GeO2 electrode shows
a low coulombic efficiency in the first cycle (43%), which is mainly caused by a poor Ge oxidation kinetics
(Ge + 2Li2O→GeO2 + 2Li+ +2e−). The X-ray absorption spectroscopy (XAS) data illustrate that the Cu
component in CuGeO3 is converted to nano-sized metallic Cu in the earlier stage of lithiation but idles
thereafter. In contrast, the Ge component in CuGeO3 behaves like the GeO2 electrode. It is converted to
nano-sized Ge by a conversion reaction and further lithiated by alloying reaction. The de-lithiation proceeds
in the reverse order. The CuGeO3 electrode shows a much improved coulombic efficiency (74%) in
the first cycle, which is indebted to a facilitated Ge oxidation with a much reduced electrode polarization.
This feature has been explained by the favorable roles provided by the in situ generated nano-sized
metallic Cu particles that make such an intimate contact with the nano-sized Ge and Li2O that they can
catalyze Li2O decomposition and provide an electronic conductive network for Ge oxidation. A similar
favorable effectwas observed with the other ternary oxides (FeGeO3 and CoGeO3), wherein the formation
of nano-sized metallic Fe and Co can be assumed.
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College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Chemical and Biological Engineering (화학생물공학부)Journal Papers (저널논문_화학생물공학부)
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