X-ray spectroscopic studies of secondary battery materials.
Item
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Title
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X-ray spectroscopic studies of secondary battery materials.
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Identifier
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AAI9908336
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identifier
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9908336
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Creator
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Kostov, Svilen Dimitar.
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Contributor
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Adviser: Marten denBoer
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Date
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1998
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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 | Energy
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Abstract
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X-ray spectroscopic methods, both NEXAFS and EXAFS were used in the study of the structural and electronic properties of different types of new battery materials.;NEXAFS analysis of the spectra of {dollar}\rm Li\sb{lcub}1-x{rcub}{dollar}CoO2 secondary battery cathodes revealed that the addition of Li proceeds is strongly correlated to the increase in electronic charge on the Co ion. A structural phase transition is confirmed for {dollar}x=0.5.{dollar} The presence of Mn{dollar}\sp{lcub}+2{rcub}{dollar} is detected in the conventionally made LiMnO{dollar}\sb2{dollar} cathodes but not in ones prepared according to the new ADL process.;{dollar}\rm Li\sb{lcub}x{rcub}V\sb6O\sb{13}{dollar} cathode material, where {dollar}0\le x\le6,{dollar} was measured using x-ray absorption, EPR and NMR techniques. The intercalation mechanism involves a conversion of V{dollar}\sp{lcub}+5{rcub}{dollar} to V{dollar}\sp{lcub}+4{rcub}{dollar} in {dollar}\rm V\sb6O\sb{13}{dollar} until the composition {dollar}\rm Li\sb2V\sb6O\sb{13}{dollar} is reached. Further addition of lithium is accompanied by the conversion of V{dollar}\sp{lcub}+4{rcub}{dollar} to V{dollar}\sp{lcub}+3{rcub}{dollar} until {dollar}\rm Li\sb8V\sb6O\sb{13}{dollar} is reached. The process is complicated and involves structural phase changes and increasing structural disorder within the multi-phase system as Li concentration is increased.;Studies of LiNi/CoO{dollar}\sb2{dollar} intercalation cathodes prepared by a novel sol-gel technique suggests that although the partial substitution of Co for Ni stabilizes the system by removing Ni{dollar}\sp{lcub}+2{rcub},{dollar} a Jahn-Teller type structural distortion in the predominantly Ni{dollar}\sp{lcub}=3{rcub}{dollar} system persists.;In-situ EXAFS measurements of the pyrite cathode in a new Li/CPE/FeS{dollar}\sb2{dollar} showed two distinct environments of the Fe ion, which were interpreted as those of metallic Fe and residual FeS{dollar}\sb2{dollar} at high lithium concentration, and {dollar}\rm Li\sb2FeS\sb2{dollar} and residual FeS{dollar}\sb2{dollar} at low lithium concentration. The formation of FeS was not detected.;A new type of hydrogen ion battery incorporating a {dollar}\rm MnSO\sb4\sp{lcub}\*{rcub}H\sb2O{dollar} based cathode and polymer electrolyte was also studied. Heavily cycled and discharged cathodes showed an almost identical Mn local structure to that of single cycled ones. The Mn environment becomes very different in the charged cathodes, due to a highly reversible chemical change. Formation of Mn+4 at the expense of Mn+3, upon charging is an unexpected result. Mn+7 does not appear to be created in this process.
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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.
