Structural Stability of LiCoO2 at 400°C |
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Authors: | Y Shao-Horn SA HackneyAJ Kahaian MM Thackeray |
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Institution: | a Department of Materials Science and Engineering, Michigan Technological University, Houghton, Michigan, 49931b Electrochemical Technology Program, Chemical Technology Division, Argonne National Laboratory, Argonne, Illinois, 60439 |
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Abstract: | The relative stability of the lithiated-spinel structure, Li2Co2]O4, at 400°C to the layered LiCoO2 structure has been investigated. “Low-temperature” LT-LiCoO2 samples were synthesized at 400°C by the solid-state reaction of Li2CO3 with CoCO3 (or Co3O4) for various times between 10 min and 232 days. Least-squares refinements of X-ray powder diffraction patterns were used to determine the fractions of lithiated-spinel Li2Co2]O4 and layered LiCoO2 in the samples. X-ray powder diffraction and transmission electron microscope data show that Li2Co2]O4 nucleates from an intermediate LixCo1−xCo2]O4 spinel product before transforming very slowly to layered LiCoO2. The experimental data confirm the theoretical prediction that layered LiCoO2 is thermodynamically more stable than the lithiated-spinel structure at 400°C and support the arguments that a non-ideal cation distribution in Li2Co2]O4, non-stoichiometry and kinetic factors restrict the transformation of the lithiated-spinel structure to layered LiCoO2 at this temperature. |
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Keywords: | lithium-cobalt-oxide spinel structure phase transition X-ray diffraction transmission electron microscopy electron diffraction lithium batteries |
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