Revealing lithium–silicide phase transformations in nano-structured silicon-based lithium ion batteries via in situ NMR spectroscopy

Ogata, Ken; Salager, Elodie; Kerr, C. J.; Fraser, AE; Ducati, Caterina; Morris, Andrew J.; Hofmann, Stephan; Grey, Clare P.

doi:10.1038/ncomms4217

Cited by 348 publications

(447 citation statements)

References 51 publications

(131 reference statements)

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“…These structures serve as a model for the clustering and bonding behavior of electrochemically lithiated silicon and germanium. 71 The Li-Si system was used to validate our method: DFT finds all of the known phases as local energy minima including independently uncovering the Li 17 Si 4 phase. For the LiGe system, DFT finds Li 5 Ge 2 , Li 8 Ge 3 , Li 13 Ge 5 and Li 13 Ge 4 locally stable and, to the best of our knowledge, these have not been presented in the literature before.…”

Section: Discussionmentioning

confidence: 99%

Thermodynamically stable lithium silicides and germanides from density functional theory calculations

Morris¹,

Grey²,

Pickard³

2014

Phys. Rev. B

113

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High-throughput density-functional-theory (DFT) calculations have been performed on the Li-Si and Li-Ge systems. Lithiated Si and Ge, including their metastable phases, play an important technological rôle as Liion battery (LIB) anodes. The calculations comprise structural optimisations on crystal structures obtained by swapping atomic species to Li-Si and Li-Ge from the X-Y structures in the International Crystal Structure Database, where X={Li,Na,K,Rb,Cs} and Y={Si,Ge,Sn,Pb}. To complement this at various Li-Si and Li-Ge stoichiometries, ab initio random structure searching (AIRSS) was also performed. Between the ground-state stoichiometries, including the recently found Li 17 Si 4 phase, the average voltages were calculated, indicating that germanium may be a safer alternative to silicon anodes in LIB, due to its higher lithium insertion voltage. Calculations predict high-density Li 1 Si 1 and Li 1 Ge 1 P4/mmm layered phases which become the ground state above 2.5 and 5 GPa respectively and reveal silicon and germanium's propensity to form dumbbells in the Li x Si, x = 2.33 − 3.25 stoichiometry range. DFT predicts the stability of the Li 11 Ge 6 Cmmm, Li 12 Ge 7 Pnma and Li 7 Ge 3 P32 1 2 phases and several new Li-Ge compounds, with stoichiometries

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Section: Discussionmentioning

confidence: 99%

Thermodynamically stable lithium silicides and germanides from density functional theory calculations

Morris¹,

Grey²,

Pickard³

2014

Phys. Rev. B

113

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“…[16][17][18][19] Distinct local atomic configurations of Li and Si have been identified at different stages of lithiation.…”

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confidence: 99%

“…13 Amorphous alloy phases with different stoichiometries have been associated with features in discharge and CV curves for Si, 14,15 and their local atomic structures have been studied using nuclear magnetic resonance (NMR), XRD and Mössbauer spectroscopy. [16][17][18][19] Distinct local atomic configurations of Li and Si have been identified at different stages of lithiation.…”

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confidence: 99%

Kinetic Study of the Initial Lithiation of Amorphous Silicon Thin Film Anodes

Miao

Thompson

2018

J. Electrochem. Soc.

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The mechanisms and kinetics of lithiation and delithiation of amorphous silicon were investigated using potentiostatic techniques and thin films of different thickness, with a focus on the initial lithiation process that occurs in the first cycle. In potentiostatic tests, distinct kinks were observed in the current vs. time curves, and the time at which the kink occurred increased for thicker films. This behavior can be explained using a model in which a sharp interface between an amorphous Li x Si phase and Li-saturated amorphous Si propagates through the film. Using this model, the rate-limiting process was determined to be diffusion of Li in the Li x Si phase rather than reaction at the lithiation front. The Li diffusivity in the lithiated phase was determined to be in the 10 −13 cm 2 /s range, independent of film thickness above 135 nm. The thin-film potentiostatic technique used in this study should prove useful in investigation of the mechanisms and rate parameters for other phase transitions that occur during lithiation of silicon and for kinetic studies of other electrode materials. Li-ion rechargeable batteries have been the focus of much research and development over recent decades. They power products ranging from electric vehicles to miniaturized electronic and medical devices. Due to its largest known capacity (8375 Ah/cm 3 , 3579 Ah/kg), Si is viewed as a promising anode material for batteries with high energy and power densities. Its abundance and relatively low cost also make it a practically feasible anode material.1 However, Si anodes suffer from capacity fade due to the very large volume expansion (up to 400%) 2 that occurs during lithiation and the consequent mechanical degradation it causes.3 In storing lithium, silicon goes through a sequence of structural transitions that affect the rate at which mechanical stress develops. 4,5 This, in turn, affects the degree to which mechanical stresses can be accommodated through plastic deformation rather than fracture. 6 Hence, a detailed understanding of the nature and kinetics of structural transitions that occur during lithiation and delithiation of silicon should provide insight into means of mediating the effects of mechanical stress on the cyclability of Si anodes.Electrochemically driven reactions between Li and Si have been studied under a variety of conditions, including at elevated and room temperature. Equilibrium titration experiments at 415• C show that four crystalline lithium silicide (Li x Si) phases form (Li 12 Si 7 , Li 7 Si 3 , Li 13 Si 4 and Li 22 Si 5 ).7-9 At room temperature, however, it is found using X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) that the equilibrium crystalline Li-Si phases are absent and the crystalline Li 15 Si 4 phase is observed only at the highest levels of lithiation.10 At lower levels of lithiation, metastable amorphous phases are formed instead.11 This phenomenon is similar to chemically driven solid-state amorphization reactions, 12 which are thought to be assoc...

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“…25 The investigation of pristine Si electrodes by SECM is an indispensable step toward the understanding and characterization of the SEI at Si electrodes in general. Although only Li + electrolyte is used in this study, the lithiation is not investigated, since the potential of all Si electrodes was kept at open circuit (E S = 3.2 V) and the first lithiation requires E S ≤ 0.2 V. 26 In contrast to pristine graphite electrodes, pristine Si electrodes are covered by a native SiO 2 surface layer, which is at least 1-3 nm in thickness and possess passivating properties for many charge transfer reactions. [27][28][29] Undoped Si/SiO 2 has been used as insulating substrate for the characterization of single-walled carbon nanotubes 30,31 and gapped Au nanobands 32 by SECM.…”

mentioning

confidence: 99%

Investigation of the Electron Transfer at Si Electrodes: Impact and Removal of the Native SiO₂Layer

Bülter

Sternad

Sardinha

et al. 2015

J. Electrochem. Soc.

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Silicon is considered as one of the promising alternatives to graphite as negative electrode material in lithium-ion batteries. The electron transfer at uncharged microstructured and planar Si was characterized using the feedback mode of scanning electrochemical microscopy (SECM) and 2,5-di-tert-butyl-1,4-dimethoxybenzene as redox mediator. Approach curves and images demonstrate that the electron transfer rate constants at pristine Si are relatively small due to the native SiO 2 surface layer. In addition, the electron transfer rate constants show local variations because of the heterogeneous coverage of SiO 2 . The SiO 2 layer is at least partially removed by mechanical contact and abrasion with the microelectrode probe. After SiO 2 removal by the microelectrode or by a hydrofluoric acid dip, the electron transfer rate constants increase strongly and remain heterogeneous. Moreover, the surface of the Si electrodes is at least stable over hours after SiO 2 removal. The consequences for investigating the formation of the solid electrolyte interphase (SEI) on Si are discussed. Silicon is considered as one of the promising alternatives to graphite as negative electrode material in lithium-ion batteries (LIBs). This is due to its wide abundance, low voltage and high theoretical gravimetric capacity of 3579 mAh g −1 .1 During the lithiation, the electrochemical potential of the Si electrode exceeds the stability window of the electrolyte and, consequently, the electrolyte is reductively decomposed.2 The decomposition products form a solid electrolyte interphase (SEI) covering the Si material lying beneath.3 A major challenge of Si as negative battery electrodes is the large volume change of ca. 270% 4 upon lithiation. Recurring lithiation/delithiation causes the electrode material to crack leading, in the worst case, to irreversible loss of active material. During the volume expansion non-passivated Si surfaces are expected to be exposed which are immediately covered by a SEI layer because of ongoing electrolyte decomposition. 5 Thus, similar to metallic Li electrodes the SEI layer is continuously re-formed and remains instable during each lithiation process. 6 The properties of the SEI are important for the performance of Si negative electrodes. 5,7 In order to evaluate the Si electrode performance, reliable in situ characterization of the SEI is definitely a key issue for the progress in this field. In general, scanning probe techniques are frequently applied for various aspects of battery research. 8,9 Especially atomic force microscopy (AFM) has been used to characterize in situ and ex situ the SEI at amorphous Si (a-Si) thin films, [10][11][12][13][14] Si-based thin films, 11,15 a-Si nanopillars 16 and Si nanowires. 17,18 AFM provides information about the morphology evolution and physical properties of the SEI. The present study aims at characterizing the functional properties of Si electrodes in situ by the feedback mode of scanning electrochemical microscopy (SECM), which probes the local electron transfer ra...

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Revealing lithium–silicide phase transformations in nano-structured silicon-based lithium ion batteries via in situ NMR spectroscopy

Cited by 348 publications

References 51 publications

Thermodynamically stable lithium silicides and germanides from density functional theory calculations

Thermodynamically stable lithium silicides and germanides from density functional theory calculations

Kinetic Study of the Initial Lithiation of Amorphous Silicon Thin Film Anodes

Investigation of the Electron Transfer at Si Electrodes: Impact and Removal of the Native SiO₂Layer

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Revealing lithium–silicide phase transformations in nano-structured silicon-based lithium ion batteries via in situ NMR spectroscopy

Cited by 348 publications

References 51 publications

Thermodynamically stable lithium silicides and germanides from density functional theory calculations

Thermodynamically stable lithium silicides and germanides from density functional theory calculations

Kinetic Study of the Initial Lithiation of Amorphous Silicon Thin Film Anodes

Investigation of the Electron Transfer at Si Electrodes: Impact and Removal of the Native SiO2Layer

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Product

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Investigation of the Electron Transfer at Si Electrodes: Impact and Removal of the Native SiO₂Layer