In Situ Study of Silicon Electrode Lithiation with X-ray Reflectivity

Cao, Chuntian; Steinrück, Hans‐Georg; Shyam, Badri; Stone, Kevin H.; Toney, Michael F.

doi:10.1021/acs.nanolett.6b02926

Cited by 70 publications

(100 citation statements)

References 56 publications

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“…These previous studies show SEI layers with thicknesses between 30 and 280 Å depending on the cell chemistry. Finally, recent X-ray reflectivity studies on crystalline silicon indicate a 10 nm inorganic layer at the liquid-solid interface consistent with the ranges reported previously but still unable to probe the organic structure 49 .…”

Section: Introductionsupporting

confidence: 87%

Determination of the Solid Electrolyte Interphase Structure Grown on a Silicon Electrode Using a Fluoroethylene Carbonate Additive

Veith

Doucet

Sacci

et al. 2017

Sci Rep

179

170

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In this work we explore how an electrolyte additive (fluorinated ethylene carbonate – FEC) mediates the thickness and composition of the solid electrolyte interphase formed over a silicon anode in situ as a function of state-of-charge and cycle. We show the FEC condenses on the surface at open circuit voltage then is reduced to C-O containing polymeric species around 0.9 V (vs. Li/Li+). The resulting film is about 50 Å thick. Upon lithiation the SEI thickens to 70 Å and becomes more organic-like. With delithiation the SEI thins by 13 Å and becomes more inorganic in nature, consistent with the formation of LiF. This thickening/thinning is reversible with cycling and shows the SEI is a dynamic structure. We compare the SEI chemistry and thickness to 280 Å thick SEI layers produced without FEC and provide a mechanism for SEI formation using FEC additives.

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Section: Introductionsupporting

confidence: 87%

Determination of the Solid Electrolyte Interphase Structure Grown on a Silicon Electrode Using a Fluoroethylene Carbonate Additive

Veith

Doucet

Sacci

et al. 2017

Sci Rep

179

170

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“…The Si wafer electrode was cycled at 50 µA cm −2 . The in situ electrochemical cell used for the XRR measurements was described in detail in our previous paper . The electrochemical profile obtained during the first lithiation, shown in Figures c and c, exhibits a small plateau near 0.6 V indicating initial SEI formation .…”

Section: Properties Of Sei and Lixsi Layer Before And After 3 H Restmentioning

confidence: 93%

“…In the present study, we track the reaction front between Si and Li x Si, as well as the structural properties of several reaction layers formed during Si (de)lithiation using in situ XRR. XRR is a surface and interface sensitive technique that can be carried out under realistic electrochemical conditions with a time resolution of minutes . Utilizing single crystal Si as a model electrode allows us to obtain sub‐nanometer resolution structural insights.…”

Section: Properties Of Sei and Lixsi Layer Before And After 3 H Restmentioning

confidence: 99%

“…A smooth phase boundary exists between the pristine silicon substrate and lithiated silicon—the roughness of the lithiation front is less than 1 nm. During this process, Li ions diffuse into the first several Si layers . We conclude that the lithiation of c‐Si is a two‐phase, reaction limited, layer‐by‐layer reaction.…”

Section: Properties Of Sei and Lixsi Layer Before And After 3 H Restmentioning

confidence: 99%

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The Atomic Scale Electrochemical Lithiation and Delithiation Process of Silicon

Cao

Steinrück

Shyam

et al. 2017

Adv Materials Inter

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the lithiation and delithiation mechanisms of Si and concomitant SEI growth. In situ X-ray diffraction studies [1,7,13] have shown that crystalline silicon (c-Si) particles amorphize during lithiation, forming crystalline Li 15 Si 4 upon complete lithiation, and irreversibly amorphize during delithiation, forming amorphous silicon (a-Si). As a consequence, in the second, and all subsequent cycles, the starting electrode is amorphous as opposed to crystalline. This presents a distinct difference from graphite [14] as well as layered (intercalation) and spinel electrode materials, which typically do not undergo irreversible phase transitions. [15][16][17] Electrochemically, c-Si undergoes lithiation around 0.1 V resulting in a well-defined voltage plateau, while a-Si has multiple sloping lithiation plateaus between 0.4 and 0.1 V. [1,7,13] Transmission electron microscopy (TEM) investigations of crystalline [8,9,11] and amorphous [10,12] Si nanoparticles have reported different mechanisms for Li insertion and extraction, and have unraveled differences between pristine a-Si and a-Si formed from the delithiation of Li x Si. Nevertheless, questions concerning the atomic scale reaction process and (de) lithiation mechanism of a-Si remain unanswered. For example, is the lithiation of a-Si a single-or two-phase reaction? Is this process Li ion diffusion or reaction rate limited, and what role does the SEI play? To address these questions, we exploited in situ X-ray reflectivity (XRR) to study two cycles of lithiation and delithiation of single crystalline Si (100) electrodes, initially terminated with a thin native oxide. A fundamental understanding of these processes at the atomic scale is important, since it will improve our foundational knowledge of basic principles underlying electrochemical reactions of ions with crystalline and amorphous materials. Furthermore, such insights are imperative in order to provide strategies to mitigate irreversible capacity loss in Si anodes.It is now well-established that the SEI is formed as the result of electrolyte decomposition at the anode surface and is an electrically insulating but ionically conducting layer. [18,19] Its passivating nature in general prohibits further electrolyte decomposition. It is a chemically complex, inhomogeneous surface layer with an inner part, at the electrode/SEI interface, mostly containing inorganic components that block electrolyte transport and ingress, and an outer part, at the SEI/electrolyte interface made up of mainly organic species. [20][21][22] The inner part of the SEI is mainly composed of inorganic Li compounds such as Li-silicates, Li 2 CO 3 , Li 2 O, LiF, and LiOH; [23,24] the outer While silicon (Si) has tenfold capacity of commercially used graphite, its application is still limited due to its limited cyclability. In this in situ X-ray reflectivity study, a detailed mechanistic model of the first two (de)lithiation processes of a silicon wafer is presented, which sheds light onto the fundamental difference of the reaction of Li ions ...

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“…In recent years, a lot of research focused on the initial cycle of silicon electrodes to investigate the formation mechanism at the very starting of battery operation, which can accelerate the understanding of the usually observed large irreversible capacity loss. [36][37][38][39][40] Edström and co-workers demonstrated the interfacial mechanisms during charge and discharge, including surface silicon oxide change transformation, Li−Si alloying reaction, and formation of SEI layer. [41] As shown in Figure 3a, at the very beginning of discharge (0.5 V vs Li + /Li), a thin SEI layer has already formed but lithium has not yet reacted with silicon.…”

Section: Initial Coulombic Efficiencymentioning

confidence: 99%

Challenges and Recent Progress in the Development of Si Anodes for Lithium‐Ion Battery

Jin

Zhu

et al. 2017

Advanced Energy Materials

802

580

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Silicon, because of its high specific capacity, is intensively pursued as one of the most promising anode material for next‐generation lithium‐ion batteries. In the past decade, various nanostructures are successfully demonstrated to address major challenges for reversible Si anodes related to pulverization and solid‐electrolyte interphase. However, the electrochemical performance is still limited by challenges that stem from the use of nanomaterials. In this progress report, the focus is on the challenges and recent progress in the development of Si anodes for lithium‐ion battery, including initial Coulombic efficiency, areal capacity, and material cost, which call for more research effort and provide a bright prospect for the widespread applications of silicon anodes in the future lithium‐ion batteries.

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In Situ Study of Silicon Electrode Lithiation with X-ray Reflectivity

Cited by 70 publications

References 56 publications

Determination of the Solid Electrolyte Interphase Structure Grown on a Silicon Electrode Using a Fluoroethylene Carbonate Additive

Determination of the Solid Electrolyte Interphase Structure Grown on a Silicon Electrode Using a Fluoroethylene Carbonate Additive

The Atomic Scale Electrochemical Lithiation and Delithiation Process of Silicon

Challenges and Recent Progress in the Development of Si Anodes for Lithium‐Ion Battery

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