Nuclear magnetic resonance studies of solid state lithium ion battery materials.
Item
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Title
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Nuclear magnetic resonance studies of solid state lithium ion battery materials.
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Identifier
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AAI9946228
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identifier
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9946228
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Creator
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Wang, Yifeng.
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Contributor
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Adviser: Steve G. Greenbaum
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Date
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1999
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Condensed Matter | Physics, Nuclear | Physics, Atomic | Energy
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Abstract
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A variety of materials used in lithium ion battery development have been investigated by solid State 6,7Li NMR.;In lithiated hard carbon, 7Li high-resolution NMR measurements reveal two distinct insertion mechanisms, one is intercalation between disordered graphene planes and the other is covalently bonded with in amorphous hydrogen-containing regions of the carbon. The irreversible portion of the Li, which constitutes the solid electrolyte interface (SEI), was detected. 7Li NMR results of lithiated natural graphite and mildly oxidized graphite show that the SEI formation is more efficient in latter, and that there is excess reversible capacity not associated with intercalated Li.;With measurements of electrochemically lithiated SnO by NMR, Li 2O and LixSn phases were detected at low and intermediate Li contents, and the Lix-2Sn alloy structure is significantly different at high Li content.;6,7Li NMR spectroscopic measurements of Li1+yCoO 2 (y = 0.08, 0.35) suggest that only a small fraction (about 10% of the excess Li) may be reversible, the remainder of the excess are various impurities.;For physical mixtures of LiI and nano-scale particles of Al2O 3, the high resolution (MAS) NMR method clearly resolves two or more distinct Li+ sites, one characteristic of bulk LiI and the rest associated with surface/interface regions.;Composite solid electrolytes based on PEO, LiI and high surface area inorganic oxides were investigated. The MAS NMR spectrum of a sample with a PEO/Li ratio of 3/2 is consistent with at least two Li environments, one solvated by the polymer and one in small ionic clusters at room temperature. The Li environment becomes more purely ionic as the polymer-associated peak vanishes above 80°C.;6,7Li NMR results in Li-Co-Ni-O and Li-(Cr, Fe)-Mn-O sample systems are also presented.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
