Electrochemical Scanning Tunneling Microscopy Observation of Highly Oriented Pyrolytic Graphite Surface Reactions in an Ethylene Carbonate-Based Electrolyte Solution

Inaba, Masaaki; Siroma, Zyun; Funabiki, Atsushi; Ogumi, Zempachi; Abe, Takeshi; Mizutani, Youichi; Asano, Masaharu

doi:10.1021/la950848e

Cited by 173 publications

(116 citation statements)

References 28 publications

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“…Recent visualization studies of SEI morphology by scanning electron microscopy ͑SEM͒, 15 transmission electron microscopy ͑TEM͒, 16 scanning tunneling microscopy ͑STM͒, 17,18 and atomic force microscopy ͑AFM͒ 19 support this physical picture. SEM, TEM, and AFM images of graphitic carbon anodes cycled in ''good'' electrolytes ͑e.g., 1.0 M LiPF 6 or LiClO 4 in 1:1 by weight mixtures of ethylene carbonate and dimethyl carbonate, EC and DMC͒ provide direct visual evidence of SEIs having lateral uniformity across the carbon surface with thicknesses up to tens of nanometers and little gross porosity.…”

mentioning

confidence: 95%

Solvent Diffusion Model for Aging of Lithium-Ion Battery Cells

Ploehn

Ramadass

White

2004

J. Electrochem. Soc.

377

306

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This work presents a rigorous continuum mechanics model of solvent diffusion describing the growth of solid-electrolyte interfaces ͑SEIs͒ in Li-ion cells incorporating carbon anodes. The model assumes that a reactive solvent component diffuses through the SEI and undergoes two-electron reduction at the carbon-SEI interface. Solvent reduction produces an insoluble product, resulting in increasing SEI thickness. The model predicts that the SEI thickness increases linearly with the square root of time. Experimental data from the literature for capacity loss in two types of prototype Li-ion cells validates the solvent diffusion model. We use the model to estimate SEI thickness and extract solvent diffusivity values from the capacity loss data. Solvent diffusivity values have an Arrhenius temperature dependence consistent with solvent diffusion through a solid SEI. The magnitudes of the diffusivities and activation energies are comparable to literature values for hydrocarbon diffusion in carbon molecular sieves and zeolites. These findings, viewed in the context of recent SEI morphology studies, suggest that the SEI may be viewed as a single layer with both micro-and macroporosity that controls the ingress of electrolyte, anode passivation by the SEI, and cell performance during initial cycling as well as long-term operation.

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mentioning

confidence: 95%

Solvent Diffusion Model for Aging of Lithium-Ion Battery Cells

Ploehn

Ramadass

White

2004

J. Electrochem. Soc.

377

306

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“…The surface modification or fluorination of graphite [1][2][3] has been assumed to yield important electrode modifications by Tressaud et al, 4 i.e., Surface oxygen is reduced to some extent. The surface area of the electrode material is increased, with a subsequent increase of metal-ion intercalation and/or adsorption in the electrode.…”

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confidence: 99%

Green Fluorination of Natural Graphite and its Application in Rechargeable Magnesium Ion Transfer Battery

Rani

Rushi

Kanakaiah

et al. 2011

J. Electrochem. Soc.

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For the first time, natural graphite is successfully fluorinated electrochemically using triethylamine tri(hydrofluoride) (C 2 H 5 ) 3 N.3HF adduct. The nature of the C-F bond formed in graphite fluoride is deduced from FT-IR, Raman and XPS spectroscopy. Electrochemical discharge of the semi-ionic fluorinated graphite as cathode in magnesium cell is investigated and the discharge capacity of the C-F electrode is found to be 548 mAh/g. Graphite-fluorine cathode prepared by this procedure showed rechargeable nature in combination with magnesium anode. Fluorine based materials have a prominent place in energy storage and conversion systems. Its use stems from the intrinsic stability and ability to generate high electrochemical energy as electrodes. These attributes are direct result of the extraordinary electro negativity of fluorine and exceptionally high free energy of formation of fluorides.The surface modification or fluorination of graphite 1-3 has been assumed to yield important electrode modifications by Tressaud et al.,4 i.e., Surface oxygen is reduced to some extent. The surface area of the electrode material is increased, with a subsequent increase of metal-ion intercalation and/or adsorption in the electrode. This latter property may be due to two factors: (i) an increase in the structural disorder caused by fluorination which probably diminishes the length of the graphitic domains and induces the formation of surface nanopores in which excess metal can be accommodated.Graphite fluorides have been studied as cathode materials in lithium 5-8 or aluminum batteries 9 Nakajima et al. 10 had shown that a low fluorination of graphite can improve the capacitance of C-F in Li battery system during the insertion into the resulting materials in comparison with graphite. As a matter of fact the treated graphite samples, which contain small amounts of fluorine (0.5-3.7 atom %), exhibit discharge capacities of about 380 mAh/g. Giraudet et al. 11 had reported the preparation method of semi-ionic graphite fluoride material and used in lithium battery system, which showed a capacitance value of 530 mAh/g. Rechargeable metal-ion batteries are well adapted for portable electronic devices, research in this field mostly concerns lithium intercalation batteries. These batteries have two major limitations, cost of the battery and their environmental impact. Magnesium is an appropriate alternative for lithium, because it is less harmful and naturally more abundant than lithium.Preliminary work on Mg/graphite fluoride system 12 showed that graphite fluorides could be an interesting cathode for magnesium ion-transfer batteries, 13-17 the graphite fluoride used was prepared from iodine fluoride, hydrogen fluoride and fluorine gas. The nature of C-F bond in the graphite fluoride prepared by this method was covalent. One of reasons for poor efficiency of the system was difficult diffusion of Mg 2þ into the graphite fluoride material due to hindering of the IF z species in the material.Fluorine-graphite intercalation compounds...

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“…In-situ, electrochemical scanning probe microscopy (EC-SPM) has been previously employed to study growth of the solid-electrolyte interphase (SEI) on graphite anodes 114,115,116 and LiMn 2 O 4 thin films 117 . The ability to control the electrode potential while simultaneously imaging in electrolytes of interest allows a direct measurement of changes in the surface morphology during cycling.…”

Section: Sectionmentioning

confidence: 99%

Surface engineering of electrospun fibers to optimize ion and electron transport in Li%2B battery cathodes.

Bell¹,

Missert²,

Leung³

et al. 2012

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This report documents research into the fabrication of Lithium Manganese Oxide (Spinel) (LMO) cathode material in the form of fibrous mats, the degradation process of this material in a battery electrolyte, the formation of core-shell coated fibers and the electrochemical properties of the active cathode core fiber. In practice, LMO experiences several degradation mechanisms ranging from capacity fading, the Jahn-Teller distortion phenomenon leading to dissolution in the electrolyte phase, and the formation of surface films by degradation of the electrolyte, and/or phase transitions at the surface to form Mn 2 O 3 . Density Functional Theory (DFT) was applied to model from first principles the interactions between the electrolyte and the surface leading to Mn ion dissolution. Thermodynamic values of solvation energy were calculated and related to the applied potential on the material during electrochemical cycling. Direct in situ observation of the degradation process was conducted on fiber structures using AFM and coin cell measurements, showing the rapid formation of theorized surface films. This provides the first direct evidence of processes occurring at the interface, such as dissolution of the active material, facet development, decomposition of the electrolyte to form a surface electrolyte interface (SEI) layer, or the 4 formation of Li alcoxides/carboxylates. Methods for fabricating fiber structures of LMO were researched using two techniques; electrospinning and forcespinning. Chemical precursors were evaluated and optimized to lead to polycrystalline, hollow fibers of LMO, as well as tetragonal zirconia fiber mats. Sol-gel chemistries for the synthesis of LMO and zirconia have been implemented to generate these fiber morphologies. Core-shell methods were attempted using both techniques, proving partial success and insight into the physics of coherent core-shell fibers.The knowledge developed in this program has increased understanding of the degradation mechanisms of the active energy storage material, and aided development of a protective interface which resists these processes while permitting rapid Li + transport, good e -conductivity, a stable interface, and prevention of the formation of a solid-electrolyte interphase (SEI) layer. 5

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Electrochemical Scanning Tunneling Microscopy Observation of Highly Oriented Pyrolytic Graphite Surface Reactions in an Ethylene Carbonate-Based Electrolyte Solution

Cited by 173 publications

References 28 publications

Solvent Diffusion Model for Aging of Lithium-Ion Battery Cells

Solvent Diffusion Model for Aging of Lithium-Ion Battery Cells

Green Fluorination of Natural Graphite and its Application in Rechargeable Magnesium Ion Transfer Battery

Surface engineering of electrospun fibers to optimize ion and electron transport in Li%2B battery cathodes.

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