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Permanent link (DOI): https://doi.org/10.7939/R39Z90M2R

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High Performance Germanium-based Anode Materials for Lithium-ion and Sodium-ion Rechargeable Batteries Open Access

Descriptions

Other title
Subject/Keyword
Nanowire
Tin Sn
Germanium Ge
SEI
Lithium-ion Battery LIB
Antimony Sb
Li segregation
TEM
FIB
Anode
Thin film
Sodium-ion Battery NIB NaB SIB
TOF SIMS
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Farbod, Behdokht
Supervisor and department
Mitlin, David (Chemical and Materials Engineering)
Examining committee member and department
Li, Zukui (Chemical and Materials Engineering)
Nazemifard, Neda (Chemical and Materials Engineering)
Chung, Hyun-Joong (Chemical and Materials Engineering)
Department
Department of Chemical and Materials Engineering
Specialization
Materials Engineering
Date accepted
2014-09-23T15:12:04Z
Graduation date
2014-11
Degree
Master of Science
Degree level
Master's
Abstract
In this thesis the electrochemical performance of germanium nanowires (GeNWs) as anode for lithium-ion batteries (LIBs) and tin-germanium-antimony (Sn-Ge-Sb) thin films as anode for sodium-ion batteries (NIBs) have been investigated. Scientific literature shows a substantial study-to-study variation in the electrochemical lithiation performance of "1-D" nanomaterials such as Si and Ge nanowires or nanotubes. In chapter 2 of this thesis, we varied the vapor-liquid-solid (VLS) growth temperature and time, resulting in nanowire arrays with distinct mass loadings, mean diameters and lengths, and thicknesses of the parasitic Ge films that are formed at the base of the array during growth. When all the results were compared, a key empirical trend to emerge was that increasing active material mass loading drastically degraded the electrochemical performance. For instance, GeNWs grown for 2 minutes at 320 °C (0.12 mg cm-2 mass loading, 34 nm mean nanowire diameter, 170 nm parasitic film thickness) had a reversible capacity of 1405 mAh g-1, a cycle 50 coulombic efficiency (CE) of 99.9%, a cycle 100 capacity retention of 98%, and delivered ~ 1200 mAh g-1 at 5C. To contrast, electrodes grown for 10 minutes at 360°C (0.86 mg cm-2, 115 nm, 1410 nm) retained merely 5.6% of their initial capacity after 100 cycles, had a CE of 96%, and delivered ~ 400 mAh g-1 at 5C. Using TOF-SIMS we are the first to demonstrate marked segregation of Li to the current collector interface in planar Ge films that are 300 and 500 nm thick, but not in the 150 nm specimens. FIB analysis shows that the cycled higher mass loaded electrodes develop more SEI and interfacial cracks near the current collector. A comparison with the state-of-the-art scientific literature for a range of Ge - based nanostructures shows that our low mass loaded GeNWs are highly favorable in terms of the reversible capacity at cycle 1 and cycle 100, steady-state cycling CE and high-rate capability. Chapter 3 provides the first report on several compositions of ternary Sn-Ge-Sb thin film alloys for application as sodium ion battery (aka NIB, NaB or SIB) anodes, employing Sn50Ge50, Sb50Ge50 and pure Sn, Ge, Sb as baselines. Sn33Ge33Sb33, Sn50Ge25Sb25, Sn60Ge20Sb20 and Sn50Ge50 all demonstrate promising electrochemical behavior, with Sn50Ge25Sb25 being the best overall. This alloy has an initial reversible specific capacity of 833 mAhg-1 (at 85 mAg-1), and 662 mAhg-1 after 50 charge - discharge cycles. Sn50Ge25Sb25 also shows excellent rate capability, displaying a stable capacity of 381 mAhg-1 at a current density of 8500 mAg-1 (~ 10C). A survey of published literature indicates that 833 mAhg-1 is among the highest reversible capacities reported for a Sn-based NIB anode, while 381 mAhg-1 represents the most optimum fast charge value. HRTEM shows that Sn50Ge25Sb25 is a composite of 10 - 15 nm Sn and Sn-alloyed Ge nanocrystallites that are densely dispersed within an amorphous matrix that also contains localized "buffering" nanoporosity. Comparing the microstructures of alloys where the capacity significantly exceeds the rule of mixtures prediction to those where it does not, leads us to hypothesize that this new phenomena originates from the Ge(Sn) that is able to sodiate beyond the 1:1 Na:Ge ratio reported for the pure element. Combined TOF-SIMS, EELS TEM and FIB analysis demonstrates substantial Na segregation within the film near the current collector interface that is present as early as the second discharge, followed by cycling - induced delamination from the current collector.
Language
English
DOI
doi:10.7939/R39Z90M2R
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
"Array Geometry Dictates Electrochemical Performance of Ge Nanowire Lithium Ion Battery Anodes", Journal of Materials Chemistry A., 2014, 2 (39), 16770 – 16785"Anodes for Sodium Ion Batteries based on Tin - Germanium - Antimony Alloys", ACS Nano, 2014, 8 (5), 4415–4429

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