Structure and properties of deeply Li-doped polyacenic semiconductor materials beyond C6Li stage

Yata, Shizukuni; Kinoshita, Hajime; Komori, M.; Ando, Nobuo; Kashiwamura, Takamitsu; Harada, Tomoko; Tanaka, Kazuyoshi; Yamabe, Tokio

doi:10.1016/0379-6779(94)90306-9

Cited by 186 publications

(72 citation statements)

References 11 publications

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“…The labels A1 2 A3, Z1 2 Z3 denote the six planar Li ions which connect to the armchair edge, and zigzag edge carbon atoms, respectively, while the N Li ion is separated from the graphite plane by a large distance (10.6Å) and thus becomes a neutral atom which is easily released. 5. Actually, when we compare the total energies of the cluster given in Fig.…”

Section: LI Ions On the Clusters With Dangling Bonds: Li 7 C 96mentioning

confidence: 99%

“…In the small graphite clusters that are pyrolytically synthesized from hydrocarbons, such as poly-paraphenylene (PPP) 1,2 and phenol-formaldehyde (polyacen semiconductors, PAS), [3][4][5] the graphite cluster can accept three times as many Li ions (LiC 2 ) as the first stage Li intercalated (LiC 6 ) graphite intercalation compound (GIC). In GIC's, LiC 6 is the compound with the greatest concentration of intercalate atoms that can be introduced between graphite layers under ambient pressures, forming a p 3 3 p 3 structure of Li ions on a honeycomb lattice, as in first stage Li-GIC's.…”

Section: Introductionmentioning

confidence: 99%

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Excess Li ions in a small graphite cluster

et al. 1997

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We calculate the optimized geometry and the corresponding electronic structure of Li ions doped in a small graphite cluster with dangling bonds or hydrogen terminations at the edge surrounding the cluster. The calculations imply both covalent and ionic bonds of Li ions to carbon atoms, which may be relevant to explaining the broad signal of the 7 Li NMR Knight shift spectra. Li intercalation, in particular, is possible even at the hydrogen-terminated edges. Because of the finite size effect of the cluster, the ionicity of intercalated Li ions has a large distribution of values, ranging from positive values close to that in graphite intercalation compounds to even slightly negative values, depending on the bonding geometry. We propose that the cluster edge surface plays a special role in accommodating excess Li ions in the disordered graphite system.

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Section: LI Ions On the Clusters With Dangling Bonds: Li 7 C 96mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Excess Li ions in a small graphite cluster

et al. 1997

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“…5 When Li atoms make a strong covalent bond with the dangling bond from the carbon atom, the Li absorption process becomes irreversible in secondary batteries, which may be consistent with the irreversible portion of the discharge curve that is observed in secondary batteries. 3,12 This irreversible portion of the discharge/charge curves can also be understood by the oxidation of the surface, which is known as the solid-electrolyte interface (SEI). 15,16 As for the hydrogen-terminated edges, Nakada et al showed that there are special electronic states of the valence electrons at the Fermi energy and that these special states are localized at the so-called zigzag edges of a nanographite cluster.…”

Section: Introductionmentioning

confidence: 99%

“…Nanographite clusters, consisting of several layers of graphitic planes with a small area, are obtained by the heat treatment of various pregraphitic carbons, such as polyparaphenylene (PPP) 1,2 and pheno-formaldehyde (polyacenic semiconductors, PAS), 3,11,12 at temperatures from 700 to 900°C, where the hydrogen atoms of the precursor hydrocarbon molecules are dissociated from the carbon atoms, 13 and the nanographite is formed by connecting the dangling bonds of the carbon atoms thus generated. Another type of nanographite cluster stems from porous carbon structures, such as activated carbon fibers (ACFs) and carbon aerogels, whose specific surface areas can be as large as 3000 m 2 /g.…”

Section: Introductionmentioning

confidence: 99%

Fracture modes in brittle coatings with large interlayer modulus mismatch

et al. 1999

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Negative ion states for Li atoms are found in graphite nanoclusters heavily doped with lithium using a semiempirical calculational method. These calculations identify a quasi-stable site for a negative Li ion near the terminated hydrogen atoms, and this site becomes very stable in the presence of the Coulomb interaction between Li ions. The total charge transfer from Li ions to the graphite clusters does not depend on the number of Li atoms per cluster but rather on the relative geometries of the Li atoms on the cluster. The relationship of these findings to the findings in the 7 Li nuclear magnetic resonance experiments and to the performance of Li secondary batteries is discussed.

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“…Recently, some disordered carbons were shown to have a specific capacity much higher than that expected from the first-stage graphite intercalation compounds (C 6 Li : 372 mAh/g), where Li is most highly intercalated between each graphite sheet. [1][2][3] We have synthesized a polyacene-based oligomer by high-pressure oligomerization of diphenyldiacetylene. 3 In this study, the annealing of polyacene-based oligomer was carried out to synthesize a disordered carbon.…”

Section: Introductionmentioning

confidence: 99%

Annealing of polyacene-based oligomer synthesized under high pressure

Kojima

Matsuoka

Takahashi

1999

J. Appl. Polym. Sci.

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A polyacene-based oligomer was synthesized by reaction of diphenyldiacetylene under high pressure (pressure: 0.1 GPa; temperature: 250°C; time: 5 h). Annealing of the polyacene-based oligomer was carried out (temperature: 300 -800°C; time: 5 h). Gas analysis, BET surface area measurement, Raman scattering, X-ray diffraction, elemental analysis, 13 C-NMR, and conductivity measurements were performed to characterize the structure of the product. The oligomer was annealed with the appearance of mainly hydrogen. The H/C of the product decreased with increasing annealing temperature. The Raman band is observed at 1610 cm Ϫ1 assigned to a doubly degenerate deformation vibration of the carbon hexagonal ring. The additional band observed at 1340 cm Ϫ1 is attributed to the size effect. X-ray diffraction indicated that the product had no sharp peak because of the disordered carbon structure.

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Structure and properties of deeply Li-doped polyacenic semiconductor materials beyond C6Li stage

Cited by 186 publications

References 11 publications

Excess Li ions in a small graphite cluster

Excess Li ions in a small graphite cluster

Fracture modes in brittle coatings with large interlayer modulus mismatch

Annealing of polyacene-based oligomer synthesized under high pressure

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