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Synthesis and Electrochemical Properties of the Misfit-Layered Cobaltite Nanomaterials
|Young-Dae Ko 1,2, Jong-Sung Park 3, Jae-Gwan Park 1, Sahn Nahm 2, Dong-Wan Kim 1|
1. Korea Institute of Science and Technology, Nano-Materials Research Center, Seoul 136-791, Korea, South
We report on a preparation of nano-sized calcium cobaltite materials with good homogeneity and their detailed lithium reactivity for the application to Li-ion battery electrodes. Derived from NaxCoO2, the cobaltite, Ca3Co4O9 has a misfit structure alternating [CoO2] and [Ca2CoO3] with CdI2- and rocksalt-type layers, respectively. Compared to the carbon-based anode, transition metal oxides have an extremely large reversible capacity arising from their displacement reactions. Accordingly, we designed a series of Ca3(Co3M)O9 compounds in order to substitute cation sites in this layered structure with transition-metal, M (M = Co, Cu, and Fe). After the intermediate formation of polybasic chelates using citric acid, HOC(CH2CO2H)2×CO2H with metallic ions, each powder was successfully produced at 700oC for 2 hours in O2 atmosphere. The obtained powders show a two-dimensional morphology consisting of very thin micalike nano-platelets. We found that these cobaltite nanomaterials show excellent lithium reactivity, which results in a high reversible specific capacity. In addition, the formation of nanocomposite composed of highly dispersed transition-metal nano grains embedded into a Li2O and CaO matrix with pseudo-amorphous character is also observed during the charge/discharge process, using a high resolution transmission electron microscopy.
Presentation: Poster at E-MRS Fall Meeting 2007, Symposium A, by Dong-Wan Kim
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-12 17:09 Revised: 2009-06-07 00:44