Type
Text
Type
Dissertation
Advisor
Grey, Clare P | Khalifah, Peter | Grubbs, Robert | Cabana, Jordi.
Date
2015-05-01
Keywords
Chemistry | Alloy, Anode, Ge, Li ion Batteries, lithiation, Sn
Department
Department of Chemistry.
Language
en_US
Source
This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree.
Identifier
http://hdl.handle.net/11401/77073
Publisher
The Graduate School, Stony Brook University: Stony Brook, NY.
Format
application/pdf
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. | 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. | 184 pages
Recommended Citation
Jung, Hyeyoung, "Solid state NMR and pair distribution function analysis studies of Ge and Sn anodes for Li-ion batteries" (2015). Stony Brook Theses and Dissertations Collection, 2006-2020 (closed to submissions). 2910.
https://commons.library.stonybrook.edu/stony-brook-theses-and-dissertations-collection/2910