Structure of coke powder heat-treated with boron

Hamada, Takashi; Suzuki, Kimihito; Kohno, Taro; Sugiura, Tsutomu

doi:10.1016/s0008-6223(01)00271-8

Cited by 18 publications

(7 citation statements)

References 20 publications

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“…X-ray photoelectron spectroscopy ͑XPS͒ showed no evidence of enrichment of boron to the particle surfaces of CP-B(x) (0 Ͻ x Ϲ 5.0). Further, boron-doped coke powders heat-treated at temperatures higher than 2200°C for 1 h exhibited about 20 mAh/g of C͑1, 0.9 V͒, 17 which is equal to the maximum of C͑1, 0.9 V͒ shown in Fig. 7, implying that the samples in this study possess fairly homogeneous distributions of dissolved boron.…”

Section: Resultssupporting

confidence: 54%

“…14,15 Hamada et al prepared boron-doped pitch coke powder using an Acheson furnace, which is available in mass production of anode materials for lithium-ion secondary batteries but cannot be free from N 2 or CO 2 gas. 16,17 The obtained coke powder contained BN film on the particle surface and B 2 O 3 , and exhibited a large irreversible capacity in the first lithium dope-undope cycle. Oxidation of the BN to B 2 O 3 at 1100°C in CO 2 and the following conversion of B 2 O 3 to B 4 C at 1400 or 1600°C in Ar had less affect on the larger irreversible capacity, but heat-treatment at temperature higher than 2000°C in Ar after the oxidation of BN significantly lowered the irreversible capacity.…”

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“…These results and the concentration of dissolved boron estimated from the potential curves of the first lithium doping 12 implied that a high concentration of dissolved boron significantly reduces irreversible capacity in the first cycle, while BN, B 2 O 3 , and B 4 C have little effect on irreversible capacity. 16,17 Although dissolved boron was implied to depress the irreversible capacity of graphitized cokes, the effect of dissolved boron has not been well confirmed. The concentration of dissolved boron was not systematically changed.…”

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Irreversible and Discharge Capacities Depending on Dissolved Boron Concentration of Coke Powder

Hamada

Shoji

Kohno

et al. 2002

J. Electrochem. Soc.

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Well-graphitized coke powder was further heat-treated at 2200°C with various amounts of boron in Ar to prepare coke powders containing different amounts of dissolved boron. The particle size distribution, specific surface area, crystallite size, and the texture observed with transmission electron microscopy were less dependent on the concentration of residue boron, ͓B͔ res , after the heat-treatment. The dissolved boron concentration, ͓B͔ sol , was quantitatively estimated from the potential curve of the first lithium doping. ͓B͔ sol was equal to ͓B͔ res when ͓B͔ res Ϲ1.0 wt % and slightly decreases with the increase of ͓B͔ res when ͓B͔ res м1.0 wt %. The irreversible capacity of the first lithium dope-undope cycle monotonously decreased, became minimum at about 0.4-0.5 wt % ͓B͔ sol , and again slightly increased with the increase of ͓B͔ sol . The discharge capacity of the first cycle was monotonously raised with the increase of ͓B͔ sol . The mechanisms of irreversible capacity and discharge capacity depending on ͓B͔ sol are discussed.Boron-doped graphite powders were studied as anode materials of lithium-ion secondary batteries. Mesophase pitch-derived carbon fibers heat-treated with B 4 C exhibited higher reversible capacities in lithium dope-undope cycles. 1,2 The higher reversible capacity of boron-doped graphite powder would mainly come from the improved crystallinity by boron during heat-treatment. 1-5 Boron is believed to be dissolved in carbon materials with replacing carbon, 6-10 elevating diffusion of carbon, and increasing the crystallite size in heat-treatment, 4,5,11 while other mechanisms of improved crystallinity by boron doping have been proposed. 5,11 The effect of dissolved boron in graphite was studied electrochemically and theoretically by Dahn et al. 12 They simulated the potential curve of lithium dope of a boron-doped graphite uner the condition of small amount of lithium intercalated, assuming that boron substituted for carbon acts as an electron acceptor, lowers the Fermi level, and somewhat shifts the potential curve of lithium dope curve higher. 12 The theory has been supported by some experiments. 3,12,13 Suzuki et al. reported that pitch coke powders heat-treated with boron in Ar using a laboratory furnace possess significantly reduced irreversible capacities in the first lithium dope-undope cycle, as well as larger reversible capacities, while pitch coke graphitized without boron exhibits a larger irreversible capacity. 14,15 Hamada et al. prepared boron-doped pitch coke powder using an Acheson furnace, which is available in mass production of anode materials for lithium-ion secondary batteries but cannot be free from N 2 or CO 2 gas. 16,17 The obtained coke powder contained BN film on the particle surface and B 2 O 3 , and exhibited a large irreversible capacity in the first lithium dope-undope cycle. Oxidation of the BN to B 2 O 3 at 1100°C in CO 2 and the following conversion of B 2 O 3 to B 4 C at 1400 or 1600°C in Ar had less affect on the larger irreversible capacity, but heat...

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Section: Resultssupporting

confidence: 54%

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confidence: 99%

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confidence: 99%

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Irreversible and Discharge Capacities Depending on Dissolved Boron Concentration of Coke Powder

Hamada

Shoji

Kohno

et al. 2002

J. Electrochem. Soc.

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“…These results indicate that boron doping improves the crystallinity of carbon foams, which supports the view that boron is substitutionally positioned in the hexagonal graphitic layers. The enhancement of graphitization by substitutional boron has been extensively studied [23,39]. XPS measurements of the boron-doped foams were carried out to determine whether the replacement of carbon atoms by boron atoms had taken place.…”

Section: Boron Retention Analysismentioning

confidence: 99%

Characterisation of boron-doped coal-derived carbon foams and their oxidation behaviour

Rodríguez

Garcı́a

2012

Fuel

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Carbon foams with improved resistance to oxidation were obtained from a bituminous coal and different boron precursors (boron oxide, boron carbide, pyridine-borane complex), by controlled carbonisation under the pressure derived from the release of the volatile matter, which also acts as the foaming agent. The foams were subsequently carbonised at 1100 °C and the presence of boron gives rise to an increasing disorder in the carbon structure. After heat treatment at 2400 °C, it is confirmed that boron occupies substitutional positions in the graphitic layers, and at high boron loadings (> 2.5%), boron clusters, boron carbide and BC 2 O structures are also observed. The presence of boron has two opposite effects on the oxidation behaviour of the foams. At low B loadings, the foams obtained with boron carbide display lower oxidation temperatures. In the other foams, increases in the temperature of oxidation and the amount of residue remaining after the oxidation tests are observed.

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“…As is well known, boron atoms can be inserted into graphite to form B 4 C clusters. In addition, some boron atoms can substitute for the carbon atoms, since the atomic radius of boron is close to that of carbon, which can effectively influence the structure, electrochemical performance and physicochemical properties of graphite [5][6][7][8][9]. One prominent structural characteristic of boron-doped carbon materials is the obvious decrease in the interlayer spacing.…”

Section: Introductionmentioning

confidence: 99%

Effect of Boron Doping on the Interlayer Spacing of Graphite

Bao

Zeng

et al. 2022

Materials

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Boron-doped graphite was prepared by the heat treatment of coke using B4C powder as a graphitization catalyst to investigate the effects of the substitutional boron atoms on the interlayer spacing of graphite. Boron atoms can be successfully incorporated into the lattice of graphite by heat treatment, resulting in a reduction in the interlayer spacing of graphite to a value close to that of ideal graphite (0.3354 nm). With an increase in the catalyst mass ratio, the content of substituted boron in the samples increased significantly, causing a decrease in the interlayer spacing of the boron-doped graphite. Density functional theory calculations suggested that the effects of the substitutional boron atoms on the interlayer spacing of the graphite may be attributed to the transfer of Π electrons between layers, the increase in the electrostatic surface potential of the carbon layer due to the electron-deficient nature of boron atoms, and Poisson contraction along the c-axis.

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Structure of coke powder heat-treated with boron

Cited by 18 publications

References 20 publications

Irreversible and Discharge Capacities Depending on Dissolved Boron Concentration of Coke Powder

Irreversible and Discharge Capacities Depending on Dissolved Boron Concentration of Coke Powder

Characterisation of boron-doped coal-derived carbon foams and their oxidation behaviour

Effect of Boron Doping on the Interlayer Spacing of Graphite

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