Mapping of Redox Energies
作者:
J.B. Goodenough,
期刊:
Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals
(Taylor Available online 1998)
卷期:
Volume 311,
issue 1
页码: 1-14
ISSN:1058-725X
年代: 1998
DOI:10.1080/10587259808042359
出版商: Taylor & Francis Group
关键词: battery;lithium-ion;insertion compounds;polyanion structures
数据来源: Taylor
摘要:
Electrochemical discharge/charge curves vs Lithium of coin cells using as cathodes various transition-metal oxide hosts for lithium insertion/extraction reactions provide information on the operative redox energies of the transition-metal atoms. The relative positions of the redox energies were found to vary little, but their absolute positions by as much as 1 eV, with changes in structure or, for an isostructural series, with changes in counter cation. Use of polyanions to obtain a more open framework with a larger free volume for Li+-ion motion was found to be more important for high-power applications than the loss in electronic mobility, but a larger free volume for ionic motion reduces the capacity per unit volume. It was shown that introduction of a second phase with a higher redox energy provides a buffer against over discharge. A reversible decrease in capacity with increasing current density was identified and its origin discussed. Substitution of the polyanions (PO4)3−or (SO4)2−for oxide ions brings the V4+/V3+and Fe3+/Fe2+redox energies to levels of interest for cathodes in a lithium-ion battery.
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