Electrochemical Cycling of Sodium‐Filled Silicon Clathrate

Wagner, Nicholas; Raghavan, Rahul; Zhao, Ran; Wei, Qun; Peng, Xihong; Chan, Candace K.

doi:10.1002/celc.201300104

Cited by 31 publications

(58 citation statements)

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“…Many framework compositions have been attained, leading to new materials for potential optoelectronic, thermoelectricor electrochemical applications,, or catalytic use . Synthetic clathrates can be anionic, cationic, or neutral according to the formal charge of the lattice; apart few exceptions,, they need to contain a guest in order to be stable.…”

Section: Empty Space Architecturesmentioning

confidence: 99%

Supramolecular Organization in Confined Nanospaces

Tabacchi

2018

ChemPhysChem

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Empty spaces are abhorred by nature, which immediately rushes in to fill the void. Humans have learnt pretty well how to make ordered empty nanocontainers, and to get useful products out of them. When such an order is imparted to molecules, new properties may appear, often yielding advanced applications. This review illustrates how the organized void space inherently present in various materials: zeolites, clathrates, mesoporous silica/organosilica, and metal organic frameworks (MOF), for example, can be exploited to create confined, organized, and self-assembled supramolecular structures of low dimensionality. Features of the confining matrices relevant to organization are presented with special focus on molecular-level aspects. Selected examples of confined supramolecular assemblies - from small molecules to quantum dots or luminescent species - are aimed to show the complexity and potential of this approach. Natural confinement (minerals) and hyperconfinement (high pressure) provide further opportunities to understand and master the atomistic-level interactions governing supramolecular organization under nanospace restrictions.

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Section: Empty Space Architecturesmentioning

confidence: 99%

Supramolecular Organization in Confined Nanospaces

Tabacchi

2018

ChemPhysChem

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“…Most interesting are tetrahedral Si networks, which have been suggested (predominantly on the basis of computational results) for covalent Si allotropes, and whicha llow to keep the sp 3 hybridization of the Si atom in its ground-state modification; some with promising physicalp roperties. [3] Most of them have al ower density than a-Si and therefore can also function as possible hosts for host-guest frameworks, for example, for the use in lithium ionbatteries [4] or thermoelectric applications. [5] Lately,s everal new Si allotropes have been reported, and the efficiency of various computational structure search methods for the discovery of structures with comparably small unit cells has been demonstrated in as eries of publications.…”

Section: Silicon Seeks Another Crystal Structurementioning

confidence: 99%

“…The structure is described in space group beside the five-membered rings of the realgar unit (Figure 8a). Natural tiling leads to one [5 4 ]( realgar), two [5 2 .7 2 ], one [7 4 ], and four [5 2 .6 2 .7 2 ]p olyhedra (Figure 8a,m iddle right), with the last four symmetry-dependent polyhedra (light blue in Figure 8a,r ight) enclosing the realgar unit. The average ring size of 6.0 is equivalent to the situation in a-Si.…”

Section: Three-dimensional Silicon Network Constructed By Different mentioning

confidence: 99%

Section: Silicon Seeks Another Crystal Structurementioning

confidence: 99%

See 1 more Smart Citation

Slicing Diamond—A Guide to Deriving sp³‐Si Allotropes

Jantke

Stegmaier

Karttunen

et al. 2016

Chemistry A European J

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Silicon is the most important material for solar cells. However, its low conversion rate/quantum efficiency requires a rather high material consumption. Thus, researchers undertake enormous experimental and theoretical efforts to find alternative Si allotropes with a better efficiency and in the ideal case a direct electronic band gap. In recent years and months many new allotropic Si structures have been reported; however, they are often described incoherently and without context to existing structures. Our approach allows a classification of many of these allotropes and a relation of their structures to substructures of, for example, known Zintl phases. For this so-called "chemi-inspired" search for promising Si structures we present a "construction kit" as a guide to introducing a large number of tetrahedral Si allotropes, all derived by a modification of the pristine cubic diamond structure. In addition, this approach allows us to realize structural (topological) relationships between experimentally accessible Zintl phases of different composition, such as open tetrahedral frameworks, to a yet unknown extent, including even known phase transitions of specific Zintl phases. In topological, structural, and computational analyses (on a DFT-PBE0/SVP level of theory) we show the close relationship of ten low-energy Si structures derived from the cubic diamond modification; five of them are new, and some show quasi-direct band gaps. A simple deviation of this approach enables the construction of many more tetrahedral structures.

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“….). 25,26 Among them, NaSi and KSi phases are structurally well known, their synthesis is well documented and regularly enriched, 27 28 formation of clatrathes, [29][30][31][32] or for hydrogen storage. 33 Both phases are made of Si 4 4− tetrahedral clusters whose negative charge is balanced by alkali ions stuffed between them.…”

mentioning

confidence: 99%

Electrochemical Reactivity of KSi and NaSi Zintl Phases with Lithium

Seznéc

Senguttuvan

Larcher

et al. 2015

ECS Electrochemistry Letters

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The electrochemical reactions of NaSi and KSi Zintl phases with lithium (0-2.5 V) proceed very differently. Na/K is partially removed on first oxidation with a complete amorphization for NaSi or growth of a new crystallized K x Si phase for KSi. Upon discharge, metallic K is partially extruded and a Li-K-Si (Li 15 Si 4 -type) phase is formed. For NaSi, metallic Na is also chased on discharge but crystallization of Li-Na-Si (Li 15 Si 4 -type) phase is delayed at the second discharge. The amorphization of Li 15 K x Si 4 proceeds through a ∼0.40 Volts charge plateau but crystallized Li 15 Na x Si 4 does not show this feature and electrochemically behaves similarly to amorphous Li x Si.The design of high energy density electrochemical storage devices requires either or both high voltage difference ( E) and large amounts of exchanged species (i.e. large capacities) between the two electrodes. High E can be achieved through the use of highly electropositive metals (alkali, alkaline earth) whose corresponding monovalent or bivalent ions are either reversibly hosted in intercalation compounds (e.g. Li-ion technology) or electroplated (e.g. Li-polymer technology) during the charging step. To date, graphitic powders are the state-of-the-art intercalating material but alloys and alloying reactions have also been intensively investigated for decades with great performance improvements and some enthusiastic industrial announcements, but very slim commercialization success so far (MatsushitaWood's metal-80's, Fuji-Stalion-1995, Sony-Nexelion-2005.For Li-based systems, silicon is the most appealing candidate for Li-alloying element because it scores the highest discharge gravimetric (3579 mAh/g of Si) and volumetric (8330 mAh/cm 3 of Si) capacities, both ranking around ten times higher than those of carbon (Li 15 Si 4 1 vs. LiC 6 2 ) with a reaction taking place at very low potential (<200 mV vs. Li + /Li • ). This alloying process comes with very large volume changes 3 (≈275% for Si → Li 15 Si 4 ) leading to particle displacement, loss of contact/cohesion in composite electrodes, and formation of reactive surfaces, resulting in a poor cycle life. These major issues triggered many tackling approaches such as the use of small particles, 4,5 the confinement in active or inactive buffering matrices, 6-9 the use of suited polymeric binders, 10-15 thin films, 16-18 the application of specific cycling conditions, 19 and tuning the electrode porosity/formulation. Crystallized silicon undergoes a progressive amorphization during its first lithiation (a-Li x Si), but a crystallized phase can be spotted at very low voltage (c-Li 15 Si 4 ) and then back converted to amorphous a-Li x Si during charge.

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Electrochemical Cycling of Sodium‐Filled Silicon Clathrate

Cited by 31 publications

References 36 publications

Supramolecular Organization in Confined Nanospaces

Supramolecular Organization in Confined Nanospaces

Slicing Diamond—A Guide to Deriving sp³‐Si Allotropes

Electrochemical Reactivity of KSi and NaSi Zintl Phases with Lithium

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Electrochemical Cycling of Sodium‐Filled Silicon Clathrate

Cited by 31 publications

References 36 publications

Supramolecular Organization in Confined Nanospaces

Supramolecular Organization in Confined Nanospaces

Slicing Diamond—A Guide to Deriving sp3‐Si Allotropes

Electrochemical Reactivity of KSi and NaSi Zintl Phases with Lithium

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Slicing Diamond—A Guide to Deriving sp³‐Si Allotropes