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Analysis of Lithiation and Delithiation Kinetics in Silicon  [PDF]
Vijay A. Sethuraman,Venkat Srinivasan,John Newman
Physics , 2012, DOI: 10.1149/2.008303jes
Abstract: Analysis of lithiation and delithiation kinetics in pulse-laser-deposited crystalline thin-film silicon (Si) electrodes is presented. Data from open-circuit relaxation experiments are used in conjunction with a model based on Tafel kinetics and double-layer capacitance to estimate the apparent transfer coefficients ({\alpha}a, {\alpha}c), and exchange current density to capacitance ratio (i0/Cdl) for lithiation and delithiation reactions in a lithiated silicon (LixSi) system. Parameters estimated from data sets obtained during first-cycle amorphization of crystalline Si, as well as from cycled crystalline Si and amorphous Si thin-film electrodes do not show much variation, indicating that they are intrinsic to lithiation/delithiation in Si. A methodology to estimate the side-reaction rate and its role in the evolution of the open-circuit potential of the LixSi system are discussed. We conclude that the large potential offset between lithiation and delithiation reactions at any given state of charge is partially caused by a large kinetic resistance (i.e., small i0). Using the estimated parameters, the model is shown to predict successfully the behavior of the system under galvanostatic lithiation and delithiation.
Ferric chloride-catalyzed decarboxylative alkylation of β-keto acids with benzylic alcohols
CuiFeng Yang,Chen Shen,HaiHua Li,ShiKai Tian
Chinese Science Bulletin , 2012, DOI: 10.1007/s11434-012-5140-0
Abstract: β-Keto acids are unstable to heat, acids, and bases, and have rarely been employed as carbon nucleophiles for the formation of carbon-carbon bonds. In this context, an efficient decarboxylative alkylation reaction of β-keto acids with benzylic alcohols has been developed, for the first time, through sequential cleavage of carbon-oxygen and carbon-carbon bonds. In the presence of 10 mol% of ferric chloride, a range of β-keto acids smoothly undergo decarboxylative alkylation with benzylic alcohols to give structurally diverse unsymmetric ketones in moderate to excellent yields and with extremely high regioselectivity. Preliminary mechanistic studies indicate that the reaction proceeds through an SN1 alkylation followed by decarboxylation.
Selective oxidation of some primary and secondary benzylic alcohols to the corresponding carbonyl compounds with a Cu(III) complex
ZORICA BUGARCIC,SLOBODAN NOVOKMET,VLADAN KOSTIC
Journal of the Serbian Chemical Society , 2005,
Abstract: The selective oxidation of benzylic alcohols to the corresponding carbonyl compounds is described. In alkaline solution, the oxidation reagent potassium tetrasodium diperiodatocuprate(III) dodecahydrate (KNa4[Cu(HIO6)2]×12H2O) reacts with primary and secondary benzylic alcohols whereby good yields of the corresponding carbonyl compounds are obtained. The presented method provides for the selective oxidation of the benzylic hydroxyl group in compounds containing other types of alcoholic functional groups.
Lithiation of Tin Oxide: A Computational Study  [PDF]
Andreas Pedersen,Mathieu Luisier
Physics , 2015, DOI: 10.1021/am506108s
Abstract: We suggest that the lithiation of pristine SnO forms a layered Li$_\text{X}$O structure while the expelled tin atoms agglomerate into 'surface' planes separating the Li$_\text{X}$O layers. The proposed lithiation model widely differs from the common assumption that tin segregates into nano-clusters embedded in the lithia matrix. With this model we are able to account for the various tin bonds that are seen experimentally and explain the three volume expansion phases that occur when SnO undergoes lithiation: (i) at low concentrations Li behaves as an intercalated species inducing small volume increases; (ii) for intermediate concentrations SnO transforms into lithia causing a large expansion; (iii) finally, as the Li concentration further increases a saturation of the lithia takes place until a layered Li$_2$O is formed. A moderate volume expansion results from this last process. We also report a 'zipper' nucleation mechanism that could provide the seed for the transformation from tin oxide to lithium oxide.
Enhanced Li capacity at high lithiation potentials in graphene oxide  [PDF]
Maria E. Stournara,Vivek B. Shenoy
Physics , 2011,
Abstract: We have studied lithiation of graphene oxide (GO) as a function of oxygen coverage using first principles calculations. Our results show that the lithiation potentials and capacities in GO can be tuned by controlling the oxygen coverage, or the degree of reduction. We find a range of coverages where the lithiation potentials are above the solid electrolyte interface (SEI) formation threshold, but with capacities comparable to, or larger than graphite. We observe that in highly oxidized and mildly reduced sheets, lithiation occurs through the formation of Li-O bonds, whereas at low coverages that are typical of reduced-GO (rGO) (O:C - 12.5 %), both Li-O bonds and LiC6 configurations are observed. The covalent Li-O bond is much stronger than the bonds formed in the LiC6 ring and the lithiation potentials for epoxides at high and medium coverages are generally large (> 1 eV). For these congifurations, as in the case of Li4Ti5O12 anodes, there will be no formation of SEI, but with the additional advantage of having higher lithium storage capacity than Li4Ti5O12. In reduced GO sheets, the presence of residual oxygen atoms allows for formation of covalent Li-O bonds that lead to storage capacities and lithiation potentials higher than that of graphite. Finally, our calculations show high lithiation potentials for the edges of graphene nanoribbons, which will impede the formation of SEI and hence lead to large reversible capacity.
Stress Evolution in Composite Silicon Electrodes during Lithiation/Delithiation  [PDF]
Vijay A. Sethuraman,Annam Nguyen,Michael J. Chon,Siva P. V. Nadimpalli,Hailong Wang,Daniel P. Abraham,Allan F. Bower,Vivek B. Shenoy,Pradeep R. Guduru
Physics , 2013, DOI: 10.1149/2.021306jes
Abstract: We report real-time average stress measurements on composite silicon electrodes made with two different binders [Carboxymethyl cellulose (CMC), and polyvinylidene fluoride (PVDF)] during electrochemical lithiation and delithiation. During galvanostatic lithiation at very slow rates, the stress in a CMC-based electrode becomes compressive and increases to 70 MPa, where it reaches a plateau and increases slowly thereafter with capacity. The PVDF-based electrode exhibits similar behavior, although with lower peak compressive stress of about 12 MPa. These initial experiments indicate that the stress evolution in a Si composite electrode depends strongly on the mechanical properties of the binder. Stress data obtained from a series of lithiation/delithiation cycles suggests plasticity induced irreversible shape changes in contacting Si particles, and as a result, the stress response of the system during any given lithiation/delithiation cycle depends on the cycling history of the electrode. While these results constitute the first in-situ stress measurements on composite Si electrodes during electrochemical cycling, the diagnostic technique described herein can be used to assess the mechanical response of a composite electrode made with other active material/binder combinations.
Studies of the first lithiation of graphite materials by electrochemical impedance spectroscopy
Quanchao Zhuang,Zuofeng Chen,Quanfeng Dong,Yanxia Jiang,Ling Huang,Shigang Sun
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-1055-y
Abstract: First lithiation of graphite electrode in 1 mol/L LiPF6-EC:DEC:DMC electrolyte was investigated by electrochemical impedance spectroscopy (EIS). The results illustrated that the first arc in the high-frequency range observed in the Nyquist diagram appears near 0.9 V in the initial lithiation of graphite electrode, and its diameter increases with the decrease of polarization potential. These EIS features were attributed to the formation and growth of SEI film. Appropriate equivalent circuit was proposed to fit the experimental EIS data. The fitting results revealed the process of the formation and growth of SEI film, and evaluated quantitatively the resistance of charge transfer, as well as the capacitance of double layer along with the increase of polarization potentials.
Lithiation of InSb and Cu$_2$Sb : A Theoretical Investigation  [PDF]
S. Sharma,J. K. Dewhurst,C. Ambrosch-Draxl
Physics , 2003, DOI: 10.1103/PhysRevB.70.104110
Abstract: In this work the mechanism of Li insertion/intercalation in the anode materials InSb and Cu$_2$Sb is investigated by means of the first principles total energy calculations. The total charge densities for the lithiated products of the two compounds are presented. Based on these results the change in the bonding character on lithiation is discussed. Further, the isomer shift for InSb and Cu$_2$Sb and there various lithiated products is reported. The average insertion/intercalation voltage and volume expansion for transitions from InSb to Li$_2$InSb and Cu$_2$Sb to Li$_2$CuSb are calculated and found to be in good agreement with the experimental values. These findings help to resolve the controversy regarding the lithiation mechanism in InSb.
On plastic deformation and fracture in Si films during electrochemical lithiation/delithiation cycling  [PDF]
Siva P. V. Nadimpalli,Vijay A. Sethuraman,Giovanna Bucci,Venkat Srinivasan,Allan F. Bower,Pradeep R. Guduru
Physics , 2013, DOI: 10.1149/2.098310jes
Abstract: An in situ study of deformation, fracture, and fatigue behavior of silicon as a lithium-ion battery electrode material is presented. Thin films (100-200 nm) of silicon are cycled in a half-cell configuration with lithium metal foil as counter/reference electrode, with 1M lithium hexafluorophosphate in ethylene carbonate, diethylene carbonate, dimethyl carbonate solution (1:1:1, wt.%) as electrolyte. Stress evolution in the Si thin-film electrodes during electrochemical lithiation and delithiation is measured by monitoring the substrate curvature using the multi-beam optical sensing method. The stress measurements have been corrected for contributions from residual stress arising from sputter-deposition. An indirect method for estimating the potential errors due to formation of the solid-electrolyte-interphase layer and surface charge on the stress measurements was presented. The films undergo extensive inelastic deformation during lithiation and delithiation. The peak compressive stress during lithiation was 1.48 GPa. The stress data along with the electron microscopy observations are used to estimate an upper bound fracture resistance of lithiated Si, which is approximately 9-11 J/m^2. Fracture initiation and crack density evolution as a function of cycle number is also reported.
Studies of the first lithiation of graphite materials by electrochemical impedance spectroscopy
Quanchao Zhuang,Zuofeng Chen,Quanfeng Dong,Yanxia Jiang,Ling Huang,Shigang Sun,
ZHUANG
,Quanchao,CHEN,Zuofeng,DONG,Quanfeng,JIANG,Yanxia,HUANG,Ling,SUN,Shigang

科学通报(英文版) , 2006,
Abstract: First lithiation of graphite electrode in 1 mol/L LiPF6-EC:DEC:DMC electrolyte was investi- gated by electrochemical impedance spectroscopy (EIS). The results illustrated that the first arc in the high-frequency range observed in the Nyquist dia- gram appears near 0.9 V in the initial lithiation of graphite electrode, and its diameter increases with the decrease of polarization potential. These EIS features were attributed to the formation and growth of SEI film. Appropriate equivalent circuit was pro- posed to fit the experimental EIS data. The fitting results revealed the process of the formation and growth of SEI film, and evaluated quantitatively the resistance of charge transfer, as well as the capaci- tance of double layer along with the increase of po- larization potentials.
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