Understanding Phase Transformation in Crystalline Ge Anodes for Li-Ion Batteries

Lim, Linda Y.; Liu, Nian; Cui, Yi; Toney, Michael F.

doi:10.1021/cm501233k

Cited by 117 publications

(159 citation statements)

References 27 publications

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“…Qualitatively, the XRD patterns for Ge anodes cycled at different C-rates are similar to that in Figure 1 , but quantitatively they are different. To obtain a quantitative analysis of the XRD data, [ 8 ] the absolute crystalline phase fraction of Ge was calculated for electrodes under different C-rates and plotted against voltage and is shown in Figure 2 .…”

Section: Resultsmentioning

confidence: 99%

“…[ 6 ] In recent years, there have been a number of reports on the reaction mechanisms in Ge electrodes. [7][8][9] In situ and operando studies are more reliable than ex situ studies as the former allows us to watch the changes in the electrodes during battery operation, while the latter involves many postprocessing steps that modify the structure and chemistry of the electrodes. We previously investigated the reactions of crystalline Ge (c-Ge) electrodes cycled at C/15 using operando X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS), and proposed a reaction mechanism.…”

Section: Doi: 101002/aenm201500599mentioning

confidence: 99%

“…During delithiation, c-Li 15 Ge 4 transforms into a-Li x Ge and eventually amorphous Ge, although this transformation is incomplete, which partly explains the capacity fade. [ 8 ] In situ X-ray transmission microscopy imaging revealed a size dependent behavior of Ge particles during cycling at C/5, where smaller particles experience volume expansion before the larger ones and many small particles become inactive after one cycle. [ 9 ] A recent report used ex situ XRD, pair distribution function analyses, and in/ex situ high-resolution 7 Li solid-state nuclear magnetic resonance to investigate the fi rst lithiation cycle of c-Ge cycled at C/50.…”

Section: Doi: 101002/aenm201500599mentioning

confidence: 99%

“…This is motivated because the different C-rates affect the electrochemical reaction mechanisms and it is important to understand how these lithiation kinetics affect the reaction pathways. Different from previous work, [ 8,10 ] here we use carbon nanotubes (CNT) as the conductive additive because these provide better cycling performance, and there is no difference in the structural changes in Ge when a different conductive additive is used. [ 11 ] To the best of our knowledge, there have been no reports on utilizing operando X-ray studies on micrometer-size c-Ge particles to study and understand the dependence of the phase transformation, Li storage capacity, and cycling stability on its C-rate.…”

Section: Introductionmentioning

confidence: 99%

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Storage Capacity and Cycling Stability in Ge Anodes: Relationship of Anode Structure and Cycling Rate

Lim

Fan

Hng

et al. 2015

Advanced Energy Materials

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Operando X‐ray diffraction (XRD) and X‐ray absorption spectroscopy (XAS) studies of Ge anodes are carried out to understand the effect of cycling rate on Ge phase transformation during charge/discharge process and to relate that effect to capacity. It is discovered that the formation of crystalline Li15Ge4 (c‐Li15Ge4) during lithiation is suppressed beyond a certain cycling rate. A very stable and reversible high capacity of ≈1800 mAh g−1 can be attained up to 100 cycles at a slow C‐rate of C/21 when there is complete conversion of Ge anode into c‐Li15Ge4. When the C‐rate is increased to ≈C/10, the lithiation reaction is more heterogeneous and a relatively high capacity of ≈1000 mAh g−1 is achieved with poorer electrochemical reversibility. An increase in C‐rate to C/5 and higher reduces the capacity (≈500 mAh g−1) due to an impeded transformation from amorphous LixGe to c‐Li15Ge4, and yet improves the electrochemical reversibility. A proposed mechanism is presented to explain the C‐rate dependent phase transformations and the relationship of these to capacity fading. The operando XRD and XAS results provide new insights into the relationship between structural changes in Ge and battery capacity, which are important for guiding better design of high‐capacity anodes.

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Section: Resultsmentioning

confidence: 99%

Section: Doi: 101002/aenm201500599mentioning

confidence: 99%

Section: Doi: 101002/aenm201500599mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Storage Capacity and Cycling Stability in Ge Anodes: Relationship of Anode Structure and Cycling Rate

Lim

Fan

Hng

et al. 2015

Advanced Energy Materials

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“…Group IV elements, such as silicon, germanium, and tin as promising anode materials for the LIBs were extensively investigated by experiments and computational simulation methods 3,[5][6][7][8] . Among them, Si was paid considerable attention because of its higher theoretical specific capacity (~3579 mA h g -1 for Li 15 Si 4 at room temperature), low cost and abundant resources.…”

Section: Introductionmentioning

confidence: 99%

Atomistic Study of Lithium Ion Dynamics in Li12Si7

Shi

Wang

2015

Electrochimica Acta

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Northumbria University has developed Northumbria Research Link (NRL) to enable users to access the University's research output. Copyright © and moral rights for items on NRL are retained by the individual author(s) and/or other copyright owners. Single copies of full items can be reproduced, displayed or performed, and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided the authors, title and full bibliographic details are given, as well as a hyperlink and/or URL to the original metadata page. The content must not be changed in any way. Full items must not be sold commercially in any format or medium without formal permission of the copyright holder. The full policy is available online: http://nrl.northumbria.ac.uk/policies.html This document may differ from the final, published version of the research and has been made available online in accordance with publisher policies. To read and/or cite from the published version of the research, please visit the publisher's website (a subscription may be required.) Atomistic Study of Lithium Ion Dynamics in Li

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Carbon and Graphene Quantum Dots for Optoelectronic and Energy Devices: A Review

Rui

Song

et al. 2015

Adv Funct Materials

1,121

666

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4929wileyonlinelibrary.com organic dyes and luminescent inorganic quantum dots. In 2010, Pan et al. successfully cut graphene sheets into blue luminescent graphene quantum dots via hydrothermal route, pushing the research of luminescent carbon materials to a climax. [ 10 ] Before that, much work has been done in the fi eld of bioimaging and optical sensing [11][12][13] while little research can be found in the optoelectronic devices or energy related applications. Since 2010, attempts on multiple applications, such as photovoltaic devices, [14][15][16][17][18] light emitting diodes, [19][20][21][22] photodetectors, [ 23,24 ] photocatalysis, [ 25 ] and lithium ion batteries, [ 26,27 ] were made. CDs and GQDs are gradually emerging in these areas and improving the performance of some kinds of devices with facile methods and low cost.Actually, GQDs can be recognized as one kind of CDs, which usually possess better crystallinity than its cousins. [ 28,29 ] In spite of the controversies on the origin of luminescence due to the excitation-dependent behavior, CDs and GQDs are expected to lead to low cost solar cells and organic LEDs (OLEDs) [ 16 ] and even can improve the performance of supercapacitors [ 27 ] and lithium ion batteries (LIBs) greatly. [ 26 ] Both of them have been synthesized with various methods, including top-down and bottom-up approaches. We are not going to talk about this because some reviews have concluded them. [30][31][32] In this Feature Article, we would like to update the latest researches about the applications of CDs and GQDs in optoelectronic devices and energy related devices, as shown in Figure 1 . Besides, there are no specifi c reviews that focus on the applications of CDs and GQDs in optoelectronic devices up to date though they have been studied for several years. In the next section, we will make a brief introduction of the microstructure and optical properties of these luminescent carbon materials. Section 3 covers the multiple applications of these interesting materials. We will focus on the application for optoelectronic and energy-related devices and make a brief introduction of other applications. In Section 4, we give a perspective for CDs and GQDs, including potential applications and possible development trend. In view of several excellent reviews focusing on different aspects of CDs and GQDs, such as their synthesis, biological applications, [ 30 ] photoluminescent properties and environmental applications, we hope this article will provide valuable insights for the current statues of CDs and GQDs research in optoelectronics and energy and stimulate new ideas and further research on their potential applications. Carbon and Graphene Quantum Dots for Optoelectronic and Energy

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Understanding Phase Transformation in Crystalline Ge Anodes for Li-Ion Batteries

Cited by 117 publications

References 27 publications

Storage Capacity and Cycling Stability in Ge Anodes: Relationship of Anode Structure and Cycling Rate

Storage Capacity and Cycling Stability in Ge Anodes: Relationship of Anode Structure and Cycling Rate

Atomistic Study of Lithium Ion Dynamics in Li12Si7

Carbon and Graphene Quantum Dots for Optoelectronic and Energy Devices: A Review

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