In-Situ Lithiation/Delithiation Observation of Individual Amorphous Si Nanorods

Ghassemi, Hessam; Au, Ming; Shahbazian‐Yassar, Reza

doi:10.1017/s1431927611009184

Cited by 23 publications

(33 citation statements)

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“…41 Therefore, it is clear that lithiating a-Si is a single-phase process in conventional current density, not a two-phase reaction as observed in in situ TEM. This is consistent with the indirect experiment about the lithiation of a-Si (not via in situ TEM), 17,18 in which the appearance of a continuous change of voltage profile is believed to be the evidence of a single-phase reaction 42 (as also shown in Supporting Information Figure S1c).…”

Section: ■ Results and Discussionsupporting

confidence: 88%

“…15,16 However, many early reports state that the reaction is a one-phase reaction. 17,18 One may note that many of the observations in the literature, to date, are based on in situ TEM experiments. In TEM observations, Si (either c-Si or a-Si) is charged by large potential bias that leads to large current density (up to 30C in average) which is not feasible in a conventional LIB configuration.…”

Section: ■ Introductionmentioning

confidence: 99%

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Quantifying Electrochemical Reactions and Properties of Amorphous Silicon in a Conventional Lithium-Ion Battery Configuration

Wang

Singh

et al. 2017

Chem. Mater.

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Despite many existing studies on silicon (Si) anodes for lithium ion batteries (LIBs), many essential questions still exist on compound formation, composition, and properties. Here we show that some previously accepted findings may have limitations in reflecting the lithiation mechanisms in the conventional charging rate. Furthermore, the correlation between structure and mechanical properties in these materials has not been properly established. Here we report a rigorous and thorough study to comprehensively understand the electrochemical reaction mechanisms of amorphous-Si (a-Si) in a conventional charging rate. In-depth microstructural characterization was performed, and correlations were established between Li–Si composition, volumetric expansion, and modulus/hardness. We have found that the lithiation process of a-Si at a conventional charging rate is a single-phase reaction while it is a two-phase reaction at high rate in in situ TEM experiments. The findings in this paper establish a reference to quantitatively explain many key metrics for lithiated a-Si as anodes in real LIBs and can be used to rationally design a-Si based high-performance LIBs guided by high-fidelity modeling and simulations.

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Section: ■ Results and Discussionsupporting

confidence: 88%

Section: ■ Introductionmentioning

confidence: 99%

Quantifying Electrochemical Reactions and Properties of Amorphous Silicon in a Conventional Lithium-Ion Battery Configuration

Wang

Singh

et al. 2017

Chem. Mater.

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“…For example, although crystalline Li−Si phases are more stable than their amorphous counterparts, 38,39 a-Li x Si phases are mainly observed during the lithiation of Si, except c-Li 15 Si 4 , which is formed upon full lithiation. 40,41 We speculate that not only thermodynamics but also kinetics, carrier concentration, and so on can affect whether amorphous phases are formed during electrochemical reaction. The c-Bi/c-Mg 3 Bi 2 two-phase reaction would proceed with a migration of the interface between c-Bi and c-Mg 3 Bi 2 .…”

Section: Resultsmentioning

confidence: 97%

Fast Magnesium Ion Transport in the Bi/Mg₃Bi₂ Two-Phase Electrode

Jung

Han

2018

J. Phys. Chem. C

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Bi has recently attracted much interest as a promising Mg battery anode to replace the Mg metal, which is ideal but impractical because of instability issues associated with the electrolyte. Our first-principles molecular dynamics study addresses why the alloying reaction of Bi with Mg creates only two crystals of Bi and Mg3Bi2 and how Mg ions move in the two crystals. The formation of crystalline Mg3Bi2 is energetically much more favorable than that of amorphous Mg x Bi (0.0 ≤ x ≤ 2.5). This high thermodynamic stability of the Mg3Bi2 crystal serves as a driving force for the complete crystalline Bi/crystalline Mg3Bi2 two-phase reaction, without allowing the formation of amorphous phases typically observed in alloy-type anode materials. The Mg ions diffuse preferentially along the [001] direction in both Bi and Mg3Bi2 and diffuse about 6000 times faster in Mg3Bi2 than in Bi. Despite the relatively slow Mg transport in Bi, the absolute kinetics of Mg ions in Bi is reasonable in terms of fast battery operation. Interestingly, the calculated Mg ion diffusivity in Bi is comparable to that for a Li ion in Bi, contrary to the general perspective that multivalent ions are very sluggish compared with monovalent ions. Our study suggests that fast multivalent-ion transport can be achieved when the multivalent ion has weak bonds with the nearest host elements and exhibits small fluctuations in its coordination number and bond length during ion transport.

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“…43 The coating of a-Si does not evolve pores during delithiaion, similar to other published reports. 36,44 Li diffusion is much slower in Si than Ge 34,45 and the migration barrier for vacancies in Si is 0.45 eV, 46 which is close to the diffusion barrier of Li in Si (0.47 eV), 47 allowing for efficient vacancy migration to the surface without pore nucleation and growth. The stress induced by the Si shell on the Ge core could further slow down vacancy migration in the Ge core 48,49 and shift the threshold for pore formation to even smaller size compared to nanowires without a shell.…”

Section: ■ Introductionmentioning

confidence: 82%

Size Dependent Pore Formation in Germanium Nanowires Undergoing Reversible Delithiation Observed by In Situ TEM

Mao

et al. 2016

J. Phys. Chem. C

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Germanium (Ge) nanowires coated with an amorphous silicon (Si) shell undergoing lithiation and delithiation were studied using in situ transmission electron microscopy (TEM). Delithiation creates pores in nanowires with diameters larger than ∼25 nm, but not in smaller diameter nanowires. The formation of pores in Ge nanowires undergoing delithiation has been observed before in in situ TEM experiments, but there has been no indication that a critical diameter exists below which pores do not form. Pore formation occurs as a result of fast lithium diffusion compared to vacancy migration. We propose that a short diffusion path for vacancies to the nanowire surface plays a role in limiting pore formation even when lithium diffusion is fast.

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In-Situ Lithiation/Delithiation Observation of Individual Amorphous Si Nanorods

Abstract: Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Cited by 23 publications

References 0 publications

Quantifying Electrochemical Reactions and Properties of Amorphous Silicon in a Conventional Lithium-Ion Battery Configuration

Quantifying Electrochemical Reactions and Properties of Amorphous Silicon in a Conventional Lithium-Ion Battery Configuration

Fast Magnesium Ion Transport in the Bi/Mg₃Bi₂ Two-Phase Electrode

Size Dependent Pore Formation in Germanium Nanowires Undergoing Reversible Delithiation Observed by In Situ TEM

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In-Situ Lithiation/Delithiation Observation of Individual Amorphous Si Nanorods

Abstract: Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Cited by 23 publications

References 0 publications

Quantifying Electrochemical Reactions and Properties of Amorphous Silicon in a Conventional Lithium-Ion Battery Configuration

Quantifying Electrochemical Reactions and Properties of Amorphous Silicon in a Conventional Lithium-Ion Battery Configuration

Fast Magnesium Ion Transport in the Bi/Mg3Bi2 Two-Phase Electrode

Size Dependent Pore Formation in Germanium Nanowires Undergoing Reversible Delithiation Observed by In Situ TEM

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Fast Magnesium Ion Transport in the Bi/Mg₃Bi₂ Two-Phase Electrode