Journal
ELECTROCHIMICA ACTA
Volume 54, Issue 18, Pages 4371-4377Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.electacta.2009.03.009
Keywords
Lithium ion batteries; Anode; Metal oxide electrodes; Nano-sized metal particles; Coulombic efficiency
Categories
Funding
- Ministry of Education, Science and Technology [400-2008-0230]
- Research Center for Energy Conversion and Storage
- Ministry of Education, Science & Technology (MoST), Republic of Korea [R31-2008-000-10013-0] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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To improve the coulombic efficiency of GeO2 electrode, a Cu-containing ternary metal oxide (CuGeO3) was prepared and the electrochemical behavior of Cu component was 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 + 2Li(2)O -> 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 effect was observed with the other ternary oxides (FeGeO3 and CoGeO3), wherein the formation of nano-sized metallic Fe and Co can be assumed. (C) 2009 Elsevier Ltd. All rights reserved.
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