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Solid state NMR and pair distribution function analysis studies of Ge and Sn anodes for Li-ion batteries

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dc.contributor.advisor Grey, Clare P en_US
dc.contributor.author Jung, Hyeyoung en_US
dc.contributor.other Department of Chemistry. en_US
dc.date.accessioned 2017-09-20T16:51:51Z
dc.date.available 2017-09-20T16:51:51Z
dc.date.issued 2015-05-01
dc.identifier.uri http://hdl.handle.net/11401/77073 en_US
dc.description 184 pg. en_US
dc.description.abstract Metallic germanium and tin are attractive anode candidates in secondary lithium-ion batteries (LIBs) due to their high theoretical capacities and low operating voltages. They undergo (de) alloying processes with Li and exhibit much higher theoretical capacities, germanium (1623mAh/g) and tin (993mAh/g), compared with graphite (375mAh/g). Recently, germanium has been considered as a promising anode material for next generation LIBs due to its high capacity, fast lithium diffusion, and high electronic conductivity. Here, the (de) lithiation mechanism of micron-sized and nano-sized Ge anodes has been investigated with X-ray diffraction (XRD), pair distribution function (PDF) analysis, and in/ex situ high-resolution 7Li solid-state nuclear magnetic resonance (NMR), utilizing the structural information and spectroscopic fingerprints obtained by characterizing a series of relevant LixGey model compounds. The lithiation process of micron-sized Ge anodes involves the formation of the Li7Ge3 phase initially through a two–phase reaction process. Li7Ge3 converts to Li7Ge2 via a series of highly disordered phases, all of these phases contain columns of Li, Ge-Ge, and Ge, with the relative proportions varying as lithiation proceeds. Eventually, Li7Ge2-like short-tomeduim range environments are observed. At this point, the nucleation and growth to form crystalline Li15Ge4 occurs. Upon delithiation, a reverse conversion process occurs and finally formed amorphous Ge at the end of charge. Tin is also another promising anode material due to its high capacity and compatibility with other elements. Here, relevant LixSny model compounds (with nominal compositions Li2Sn5, LiSn, Li7Sn3, Li7Sn2, and Li22Sn5) were synthesized and characterized by XRD, 7Li/119Sn solidstate NMR and PDF analysis to assist with the identification and structural determination of the LixSny phases that form during electrochemical lithiation. These results provide insights into LixGey and LixSny phases transformation during cycling and will guide the further development of Li-alloy based anode materials for battery applications. en_US
dc.description.sponsorship This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree. en_US
dc.format Monograph en_US
dc.format.medium Electronic Resource en_US
dc.language.iso en_US en_US
dc.publisher The Graduate School, Stony Brook University: Stony Brook, NY. en_US
dc.subject.lcsh Chemistry en_US
dc.subject.other Alloy, Anode, Ge, Li ion Batteries, lithiation, Sn en_US
dc.title Solid state NMR and pair distribution function analysis studies of Ge and Sn anodes for Li-ion batteries en_US
dc.type Dissertation en_US
dc.mimetype Application/PDF en_US
dc.contributor.committeemember Khalifah, Peter en_US
dc.contributor.committeemember Grubbs, Robert en_US
dc.contributor.committeemember Cabana, Jordi. en_US

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