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Solid State Synthesis and Properties of Doped LiMnO2 Cathode Materials

Published online by Cambridge University Press:  10 February 2011

B. Ammundsen
Affiliation:
Pacific Lithium Limited, PO Box 90725, Auckland, New Zealand, brett@pacificlithiumco.nz
J. Desilvestro
Affiliation:
Pacific Lithium Limited, PO Box 90725, Auckland, New Zealand, brett@pacificlithiumco.nz
T. Groutso
Affiliation:
The University of Auckland, Private Bag 92019, Auckland, New Zealand
D. Hassell
Affiliation:
Pacific Lithium Limited, PO Box 90725, Auckland, New Zealand, brett@pacificlithiumco.nz
J. B. Metson
Affiliation:
The University of Auckland, Private Bag 92019, Auckland, New Zealand
E. Regan
Affiliation:
The University of Auckland, Private Bag 92019, Auckland, New Zealand
R. Steiner
Affiliation:
Pacific Lithium Limited, PO Box 90725, Auckland, New Zealand, brett@pacificlithiumco.nz
P. J. Pickering
Affiliation:
Pacific Lithium Limited, PO Box 90725, Auckland, New Zealand, brett@pacificlithiumco.nz
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Abstract

The crystal structures, microstructures and electrochemical properties of Al-doped lithium manganese oxide materials LiAlxMn1−xO2 (0 ≤ x ≤ 0.1) prepared by solid state reactions have been investigated. A1 doping results in increased cation disorder in the orthorhombic polymorph of LiMnO2, and produces layered monoclinic LiMnO2 with an α-NaFeO2 type crystal structure. The formation of monoclinic LiAlxMn1-xO2 confirms earlier observations by Chiang et al. [1,2]. A mechanism is proposed for the orthorhombic-monoclinic transformation, based on Li-Mn inversion in the orthorhombic structure. Al ions substitute in Mn sites in the monoclinic phase and give rise to microstrain in the [2 0 -l] planes. Microstructural analysis by scanning electron microscopy has revealed Al-deficient striations which may represent residual zones of orthorhombic phase. In cycling tests in Li button cells, increasing the amount of Al dopant extends the number of cycles required for the capacity to evolve to its maximum value, but results in increased stability of the capacity at 55 °C. The layered structure of the monoclinic materials is retained on the first cycle, but transforms to a spinel-type structure on extended cycling.

Type
Research Article
Copyright
Copyright © Materials Research Society 2000

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References

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