Charge‐Discharge Characteristics of the Mesocarbon Miocrobeads Heat‐Treated at Different Temperatures

Mabuchi, Akihiro; Tokumitsu, Katsuhisa; Fujimoto, Hiroyuki; Kasuh, Takahiro

doi:10.1149/1.2044128

Cited by 370 publications

(161 citation statements)

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“…There is no overlap 50 between Li 2s and carbon orbital energies, implying that Li completely donates its 2s electron to the carbon p z orbitals. Integrating the PDOS of MC x from E F,graphite to E F,MCx yields numbers very close to 1 for Li-, Na-and K-GICs investigated, implying virtually complete charge transfer from the alkali metal 5 atoms to the carbon. These calculations demonstrate that the alkali metals become completely ionized with a formal charge of +1 as expected from in the periodic table of the elements.…”

mentioning

confidence: 77%

“…Intercalation causes an expansion of the carbon rings, as expected from the charge transfer (see below) to the graphene layers. A larger difference between the long and short bond lengths is a possible rationalization for the lower stability of LiC 8 (NaC 8 ) compared to 5 LiC 6 (NaC 6 ). The difference between the short and long bond lengths in K-GICs is however very small.…”

Section: Discussion 1 Crystal Structure After Intercalationmentioning

confidence: 99%

“…40 Alkali metal GICs (AM-GICs) are important as electrodes in batteries, metallurgical processes and in molten salt electrolysis. Li-GIC has been actively investigated since the early of 1980s due to the discovery of the reversible electrochemical intercalation of lithium in graphite, which is widely used in 45 rechargeable lithium ion batteries [3][4][5][6][7][8][9][10]. Na-GIC has drawn attention recently due to the potential as anode in a Na-ion battery as an alternative to Li-batteries [11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

“…Semi-empirical methods based on both DFT (LDA, GGA) and empirical corrections proposed by Hasegawa et al [33] and Grimme [38,39] (vdW-D) are alternative ways to describe vdW interactions. Rydberg et al 5 have constructed a tractable non-local correlation density functionals for flat surfaces and slabs [40] and applied it to graphite and other layered structures [26,41]. Langreth and Lundqvist's non-local functional (vdW-DF) was the first to be implemented in DFT [26,[42][43][44].…”

Section: Introductionmentioning

confidence: 99%

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Van der Waals density functional study of the energetics of alkali metal intercalation in graphite

2014

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We report on the energetics of intercalation of lithium, sodium and potassium in graphite by density functional theory using recently developed van der Waals density functionals. First stage intercalation compounds are well described by conventional functionals like GGA, but van der Waals functionals is crucial for higher stage intercalation compounds and graphite, where van der Waals interactions are important. The vdW-optPBE functional gave the best agreement with reported structure and energetics 10 for graphite and LiC 6 and was further applied for intercalation of Na and K. The enthalpy of formation of LiC 6 and KC 8 were found to be -16.4 and -27.5 kJ/mol respectively. NaC 6 and NaC 8 were unstable with positive enthalpies of formation (+20.8 and +19.9 kJ/mol). The energetics of stacking of graphene and intercalant layers was investigated from first to fifth stage intercalation compounds. Higher stage compounds of Li and K were stable, but with smaller enthalpy of formation with increasing stage order. 15The higher stage Na compounds possessed positive enthalpy of formation, but less in magnitude than the energy difference of 0.6 kJ/mol between graphite with AB and AA stacking. The abnormal behaviour of the lower stage Na intercalation compounds were rationalized by the lower energy involved in the formation of the chemical bond between carbon Na relative to the corresponding bond with Li or K. The chemical bond between alkali metal and carbon is characterized by charge transfer from the alkali-metal 20 to carbon resulting in ionized alkali-metals. The intercalation induces only a subtle increase in the inplane C-C bond lengths, with longer C-C bonds in the vicinity of the alkali metals but without breaking the hexagonal symmetry.

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mentioning

confidence: 77%

Section: Discussion 1 Crystal Structure After Intercalationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Van der Waals density functional study of the energetics of alkali metal intercalation in graphite

2014

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“…This modification introduces novel properties that are beneficial to the storage capacity by removing the limitation of the capacity to 372 mAh g À1 [109][110][111][112][113][114]. Not only quantum effects, but also the increase of the number of storage sites available for the lithium ions in small closed spaces in nanostructured carbon has been proposed to explain the large capacities that have been observed [99,115,116]. One example is provided by carbon nanorings with 20 nm outer diameters and 3.5-nm wall thickness ( Fig.…”

Section: Hard Carbonmentioning

confidence: 99%

Anodes for Li-Ion Batteries

et al. 2016

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Lithium-ion batteries (LiBs) have made considerable progress since the first commercial one by Sony in 1991, which had LiCoO 2 and graphite as active elements of the positive and negative electrodes, respectively. The LiBs are now the primary energy storage devices in the transportation and communications, from portable use in computers, up to electric and hybrid vehicles. More recently, they have also been used as back-up supply units, frequency regulators (load leveling) to integrate on smart grids the electricity produced by windmills and photovoltaic plants (for a recent review, see [1]). These applications require high energy densities, high power, and safety among others. Considerable efforts have been made to propose other electrodes to fulfill these requirements. We have recently reviewed the works and progress concerning the materials for the positive electrode [2][3][4][5][6]. The present work is devoted to the materials for the negative electrode counterpart. It is common to use the terminology anode and cathode for the negative and positive electrodes, respectively, although the electrodes play alternatively the role of anode and cathode during the charge and discharge process. We shall use this terminology in the following for conciseness purposes only.An ideal active anode element should fulfill the following requirements as follows: (1) It must be light and accommodate as much Li as possible to optimize the gravimetric capacity. (2) Its redox potential with respect to Li 0 /Li + must be as small as possible at any Li-concentration. The reason is that this potential is subtracted to the redox potential of the cathode material to give the overall voltage of the cell, and smaller voltage means smaller energy density. (3) It must possess good electronic and ionic conductivities since faster motion of the lithium ions and the electrons also mean higher power density of the cell. (4) It must not be soluble in the solvents of the electrolyte and not react with the lithium salt. (5) It must be safe, i.e. avoid any thermal runaway of the battery, a criterion that is not independent of the previous one, but deserves special attention, especially for use in transportation such as electric vehicles and planes. (6) It must be cheap and environmentally friendly. The different materials proposed as anode elements for Li-ion batteries must be discussed with respect to these different criteria.The graphite is still the most used anode material and is still the reference. The first works giving evidence of the insertion of lithium in graphite date from 1955 [7], confirmed by the synthesis of LiC 6 in 1965 [8]. The synthesis of LiC 6 , however, was not obtained by electrochemical process at that time. Another decade was spent before Besenhard and Eichinger discovered the reversible intercalation of lithium in graphite, proposing this material as an anode in 1976 [9,10]. Increasing the Li content in LiC 6 is possible [8], but no reversible cycling beyond LiC 6 could ever be obtained. The graphite anode can thus be cyc...

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Electrical and electrochemical characterization of petrol cokes for lithium-ion cells

Río

Ojeda

Acosta

1999

J. Appl. Polym. Sci.

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Several cokes and graphites have been electrically and electrochemically characterized. The process of electrochemical lithium ion insertion into these materials has been analyzed for the purpose of assessing their performance as electrodes in advanced batteries and as potential candidates to substitute for lithium metal. The results obtained prove the process of electrochemical lithium ion insertion into cokes and graphites to be strongly influenced both by the ordered structure of the starting material and by the nature of the anion of the lithium salt, which is used as electrolyte.

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Charge‐Discharge Characteristics of the Mesocarbon Miocrobeads Heat‐Treated at Different Temperatures

Cited by 370 publications

References 1 publication

Van der Waals density functional study of the energetics of alkali metal intercalation in graphite

Van der Waals density functional study of the energetics of alkali metal intercalation in graphite

Anodes for Li-Ion Batteries

Electrical and electrochemical characterization of petrol cokes for lithium-ion cells

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