95 research outputs found
Lithiation of InSb and CuSb : A Theoretical Investigation
In this work the mechanism of Li insertion/intercalation in the anode
materials InSb and CuSb is investigated by means of the first principles
total energy calculations. The total charge densities for the lithiated
products of the two compounds are presented. Based on these results the change
in the bonding character on lithiation is discussed. Further, the isomer shift
for InSb and CuSb and there various lithiated products is reported. The
average insertion/intercalation voltage and volume expansion for transitions
from InSb to LiInSb and CuSb to LiCuSb are calculated and found to
be in good agreement with the experimental values. These findings help to
resolve the controversy regarding the lithiation mechanism in InSb.Comment: 5 pages 3 figure
Copper-Tin Anodes for Rechargeable Lithium Batteries: An Example of the Matrix Effect in an Intermetallic System
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Olivine Composite Cathode Materials for Improved Lithium Ion Battery Performance
Composite cathode materials in lithium ion batteries have become the subject of a great amount of research recently as cost and safety issues related to LiCoO2 and other layered structures have been discovered. Alternatives to these layered materials include materials with the spinel and olivine structures, but these present different problems, e.g. spinels have low capacities and cycle poorly at elevated temperatures, and olivines exhibit extremely low intrinsic conductivity. Previous work has shown that composite structures containing spinel and layered materials have shown improved electrochemical properties. These types of composite structures have been studied in order to evaluate their performance and safety characteristics necessary for use in lithium ion batteries in portable electronic devices, particularly hybrid-electric vehicles. In this study, we extended that work to layered-olivine and spinel-olivine composites. These materials were synthesized from precursor salts using three methods: direct reaction, ball-milling, and a coreshell synthesis method. X-ray diffraction spectra and electrochemical cycling data show that the core-shell method was the most successful in forming the desired products. The electrochemical performance of the cells containing the composite cathodes varied dramatically, but the low overpotential and reasonable capacities of the spinel-olivine composites make them a promising class for the next generation of lithium ion battery cathodes
Reciprocal Space Imaging of Ionic Correlations in Intercalation Compounds
The intercalation of alkali ions into layered materials has played an
essential role in battery technology since the development of the first
lithium-ion electrodes. Coulomb repulsion between the intercalants leads to
ordering of the intercalant sublattice, which hinders ionic diffusion and
impacts battery performance. While conventional diffraction can identify the
long-range order that can occur at discrete intercalant concentrations during
the charging cycle, it cannot determine short-range order at other
concentrations that also disrupt ionic mobility. In this article, we show that
the use of real-space transforms of single crystal diffuse scattering, measured
with high-energy synchrotron x-rays, allows a model-independent measurement of
the temperature dependence of the length scale of ionic correlations along each
of the crystallographic axes in a sodium-intercalated VO. The
techniques described here provide a new way of probing the evolution of
structural ordering in crystalline materials.Comment: 16 pages, 17 figure
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