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3. Preformed Boehmite Nanoparticles As Coating Materials for Long-Cycling LiCoO2.

Author

Fey, G. T. K., Weng, Z. X., Chen, J. G., Lu, C. Z., Kumar, T. P., Naik, S. P., Chiang, A.S.T., Lee, D.C., and Lin, J. R.

Subjects
*HYDROXIDE minerals, *BOEHMITE, *CATHODES, *NANOPARTICLES, *BAUXITE, *VOLTAMMETRY
Abstract

A simple mechano-thermal coating procedure for the production of long-cycling LiCoO2 is described. Preformed nanoparticulate boehmite was used as the coating material. The coating procedure resulted in the cathode particles covered in a 20-30 nm thick kernel of boehmite, as revealed by TEM examination. XRD studies showed that the lattice parameter c diminished upon coating, indicating that a substitutional compound of the composition LixAlyCo1-yO2 may have formed upon calcination. SEM images, R-factor values from XRD studies and galvanostatic charge-discharge studies showed that a coating level of 1.0 wt % gave an optimal performance in capacity and cyclability. SEM images showed that above the 1.0 wt % coating level, the excess boehmite adhered to the coated cathode particles as sperules. ESCA depth profile analysis showed partial diffusion of aluminum from the surface to the interior. Galvanostatic cycling studies showed that at a coating level of 1.0 wt %, cyclability improved three- and twelve-fold for the two commercial LiCoO2 samples tested. Cyclic voltammetry revealed that the hexagonal-monoclinic-hexagonal phase transformations during cycling were suppressed in the coated cathode materials. [ABSTRACT FROM AUTHOR]

Published
2004
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4. Preformed Boehmite Nanoparticles As Coating Materials for Long-Cycling LiCoO2.

Author

Fey, G. T. K., Weng, Z. X., Chen, J. G., Lu, C. Z., Kumar, T. P., Naik, S. P., Chiang, A.S.T., Lee, D.C., and Lin, J. R.

Subjects
HYDROXIDE minerals, BOEHMITE, CATHODES, NANOPARTICLES, BAUXITE, VOLTAMMETRY
Abstract

A simple mechano-thermal coating procedure for the production of long-cycling LiCoO2 is described. Preformed nanoparticulate boehmite was used as the coating material. The coating procedure resulted in the cathode particles covered in a 20-30 nm thick kernel of boehmite, as revealed by TEM examination. XRD studies showed that the lattice parameter c diminished upon coating, indicating that a substitutional compound of the composition LixAlyCo1-yO2 may have formed upon calcination. SEM images, R-factor values from XRD studies and galvanostatic charge-discharge studies showed that a coating level of 1.0 wt % gave an optimal performance in capacity and cyclability. SEM images showed that above the 1.0 wt % coating level, the excess boehmite adhered to the coated cathode particles as sperules. ESCA depth profile analysis showed partial diffusion of aluminum from the surface to the interior. Galvanostatic cycling studies showed that at a coating level of 1.0 wt %, cyclability improved three- and twelve-fold for the two commercial LiCoO2 samples tested. Cyclic voltammetry revealed that the hexagonal-monoclinic-hexagonal phase transformations during cycling were suppressed in the coated cathode materials. [ABSTRACT FROM AUTHOR]

Published
2004
Full Text
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5. Microwave-assisted solid-state synthesis of LiCoO<SUB>2</SUB> and its electrochemical properties as a cathode material for lithium batteries

Author

Subramanian, V., Chen, C. L., Chou, H. S., and Fey, G. T. K.

Abstract

Polycrystalline homogeneous lithium cobalt oxide powder was synthesized by a solid-state method using microwaves. The synthesis was carried out in a domestic microwave oven. LiCoO2 was synthesized with a microwave irradiation time of 20 min. This process remarkably reduced synthesis time and LiCoO2 was produced relatively quickly for the first time. The synthesized material showed reasonable electrochemical characteristics.

Published
2001

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