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Correlating Capacity and Li Content in Layered Material for
Li-ion Battery Using XRD and Particle size Distribution
Measurements |
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A lithiated
transition-metal oxide material was successfully synthesized by
a combustion method for Li-ion battery. The material was
characterized using thermogravimetric and particle size
analyzers, scanning electron microscope and X-ray
diffractometer. The calcined powders of the material exhibited a
finite size distribution and a single phase of pure layered
structure of space group R3¯¯¯mR3¯m . An innovative method was
developed to calculate the material electrochemical capacity
based on considerations of the crystal structure and
contributions of Li ions from specified unit cells at the
surfaces and in the interiors of the material particles. Results
suggested that most of the Li ions contributing to the
electrochemical current originated from the surface region of
the material particles. It was possible to estimate the
thickness of the most delithiated region near the particle
surfaces at any delithiation depth accurately. Furthermore,
results suggested that the core region of the particles remained
electrochemically inaccessible in the conventional applied
voltages. This result was justified by direct quantitative
comparison of specific capacity values calculated from the
particle size distribution with those measured experimentally.
The present analysis is believed to be of some value for
estimation of the failure mechanism in cathode compounds, thus
assisting the development of Li-ion batteries. |
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