Carbon Fiber Anode Research Articles

Selective Carbonylation of Methanol to Dimethyl Carbonate by Gas–Liquid–Solid-Phase Boundary Electrolysis

Abstract Selective and efficient electrochemical carbonylation of MeOH to DMC was performed over PdCl2/VGCF (vapor grown carbon fiber) anode by utilizing the three-phase boundary electrolysis at 1 atm (CO) and 298 K.

Electrochemical removal of p-nonylphenol from dilute solutions using a carbon fiber anode

p-Nonylphenol, which is widely used as raw material in industrial activities has been regarded as an environmental endocrine disrupter. In an effort to develop a new treatment method for p-nonylphenol, we initially investigated the electrochemical behavior of p-nonylphenol by voltammetric techniques. The electrochemical oxidation of p-nonylphenol led to the formation of electropolymerized film on the glassy carbon electrode surface. The fouling on the electrode surface by the electropolymerized film was evaluated by monitoring the electrode response of ferrocyanide ions as the redox marker. The electrochemical removal of p-nonylphenol based on the formation of the electropolymerized film on an anode surface was performed using a carbon fiber (CF) with a very large surface area. The high removal efficiency for p-nonylphenol was obtained by applying a potential at 0.7 V. The maximum surface coverage of electropolymerized p-nonylphenol on the CF was about 5×10 −9 mol/cm 2. The presence of humic acid hardly inhibited the removal of p-nonylphenol. Furthermore, the application to the removal of phenol, o-chlorophenol, p-chlorophenol, 2,4-dichlorophenol, and 2,4,5-trichlorophenol was attempted by using this method.

Laminated Thin Li-Ion Batteries Using a Liquid Electrolyte

Thin Li-ion batteries with a laminated film bag as a casing were developed by using a liquid electrolyte and a graphitized boron-doped mesophase-pitch-based carbon fiber (B-MCF) anode. The thin Li-ion batteries exhibited excellent discharge performance, long cycle life, and very low swelling under high-temperature storage. A 1.5 M solution of in an ethylene carbonate (EC)/γ-butyrolactone (GBL) (1:3 by volume) mixed solvent is advantageous for use as the electrolyte in the laminated film bag because of its high flame point of 129°C, high boiling point of 216°C, low vapor pressure, and high conductivity of 2.1 mS/cm at −20°C. The B-MCF anode in the electrolyte exhibited a high reversible capacity of 345 mAh/g, a high coulombic efficiency of 94% at the first cycle, and high rate capability. It was demonstrated that the thin Li-ion battery with a thickness of 3.6 mm has a high energy density of 172 Wh/kg, high rate capability between 0.2 and 3C rate discharge, a high capacity ratio of 50% at 1C rate discharge and −20°C, and a long cycle life of more than 500 cycles at 1C rate charge-discharge cycling. The B-MCF anode led to the high rate discharge performance and the long cycle life of the thin Li-ion batteries using the electrolyte. The very low swelling and small evolution of gas under the high-temperature storage at 85°C were attributable to the stability of electrolyte against the fully charged cathode material. © 2001 The Electrochemical Society. All rights reserved.

New thin lithium-ion batteries using a liquid electrolyte with thermal stability

New thin lithium-ion batteries (LIBs) using a laminated film bag, an organic liquid electrolyte, and a mesophase-pitch-based carbon fiber (MCF) anode exhibited high discharge performance, a very low swelling under a high-temperature storage, and excellent safety performance. A 1.5 M solution of LiBF 4 in an ethylene carbonate (EC)/γ-butyrolactone (GBL) mixed solvent was found to be a promising liquid electrolyte for the thin LIBs because the electrolyte has a high flame point of 129°C, a high boiling point of 216°C, a low vapor pressure, and a high conductivity of 2.1 mS/cm at −20°C. It was demonstrated that the thin LIB using B-doped MCF anode has a high energy density of 172 Wh/kg, high rate capability, high capacity at −20°C, and a long cycle life of 500 cycles. The safety of thin LIBs under overcharging tests and oven tests was superior to that of conventional prismatic LIBs and PLBs. The very low swelling and the excellent safety performance were attributable to the stability of LiBF 4–EC/GBL electrolyte against LiCoO 2 cathode material.

Li-ion polymer battery based on phase-separated gel polymer electrolyte

The characteristics of the Li ion battery based on poly(vinyl chloride)/poly(methyl methacrylate) (PVC/PMMA) polymer blend electrolyte are reported. The polymer blend electrolytes exhibited phase-separated structure which consists of a PVC-rich phase and an electrolyte-rich phase. At the constant blend ratio of PVC/PMMA=6/4, mechanical property and ionic conductivity increase with the increase of the polarity of the liquid electrolyte together with the decrease of domain size of the electrolyte-rich phase. However, these merits obtained by using the liquid electrolyte of high polarity were somewhat contrasted by the low adhesion of the corresponding polymer electrolyte toward electrode. The prototype battery cell, which consists of LiCoO 2 cathode, meso-phase carbon fiber anode and the polymer electrolyte based on PVC/PMMA=6/4 blend and 1M LiPF 6 in EC/DMC=1/1 mixture, showed the discharge capacity of 111 mAh/g (per cathode material) at charge/discharge rate of 2 C and 92% of the initial discharge capacity at 100 cycle upon the repeated charge/discharge at 0.5 C rate (0.5×complete charge/discharge in 1 h).

Electrochemical characterization of poly(ethylene- co-methyl acrylate)-based gel polymer electrolytes for lithium-ion polymer batteries

Gel polymer electrolytes (GPE) composed of poly(ethylene- co-methyl acrylate) copolymer, LiBF 4-EC/EMC/PC, and silanized fumed silica are prepared. The ionic conductivity reaches 5.8×10 −4 S cm −1 in the GPE containing 22% poly(ethylene- co-methyl acrylate), 65% LiBF 4-EC/EMC/PC and 13% silanized fumed silica at room temperature. GPEs are free-standing films and are used to prepare thin films for rechargeable lithium-ion polymer cells. Lithium-ion polymer cells, which consist of mesophase carbon fibre anode, poly(ethylene- co-methyl acrylate)-based GPE and LiCoO 2 cathode, are assembled, and their charge–discharge cycling characteristics are investigated.

Oxidation of alkanes with H2O on Ir(acac)3 supported on a carbon fiber-anode

Ir(acac)3 supported on a carbon fiber-anode catalyzed the oxidations of alkanes (cyclohexane, n-hexane, adamantane) by generating strong electrophilic oxygen species from H2O at 1.3 V (Ag|AgCl) with high current efficiency, for example, 45% for cyclohexanone formation.

Vapor-grown carbon fiber anode for cylindrical lithium ion rechargeable batteries

A lithium ion rechargeable battery based on carbon anode that is a viable replacement for lithium metal anode has been developed. In this investigation, the Vapor-Grown Carbon Fiber was used as the anode material of a cylindrical battery. The charge/discharge experiments were carried under various temperatures and current densities. Excellent cyclability was obtained at 21°C at a charge/discharge of 0.8 C with three cathode materials (LiCoO2, LiMn2O4, and LiNiO2). High discharge capacity was obtained at low temperature (0°C). Good cyclability was also obtained at high temperature (40°C). At the charge/discharge rate of 4.0 C, energy density did not decay significantly. Good cyclability was obtained for rates ranging from 0.8 C to 4.0 C. Self-discharge was investigated at 3 temperatures (21, 40 and 60°C). The measured self-discharge was 8, 15 and 31% per month at 21, 40 and 60°C, respectively.

In situ Observation of Expansion and Shrinkage of Carbon Fiber Anode during the Electrochemical Doping/Undoping of Lithium

In situ Observation of Expansion and Shrinkage of Carbon Fiber Anode during the Electrochemical Doping/Undoping of Lithium

Oxidation of Benzene to Benzoquinone during Electrolysis of Water over the Carbon Fiber-Anode

Abstract Direct oxidation of benzene to benzoquinone was performed by the electrolysis of water over the porous anodes. The porous anodes made from carbon materials, especially vapor-grown-carbon-fiber, and PTFE were active for the formation of benzoquinone. Graphite structure of carbon is essential for the electro-oxygenation of benzene with H2O

7Li-NMR study of carbon fiber and graphite anodes for lithium ion batteries

Lithium intercalation of a highly crystallized carbon fiber and natural graphite were investigated using 7Li-NMR spectroscopy. The carbon fiber having the higher crystallinity, showed resonance signals belonging to LiC x ( x>12), LiC 12, LiC 6 phases and decomposition products. The transition between these phases is fundamentally consistent with the theoretical mechanism. However, the spectra of the graphite showed an occurrence of an irregular structure in addition to these normal phases. This signal shows reversible behavior upon intercalation, and is attributed to the lithium in a turbostratic structure.

Charge-discharge behaviour of lithium ion secondary battery using graphitized mesophase pitch-based carbon fiber anodes

Mesophase pitch-based carbon fibers(MPCF) have been investigated as an anode active material for lithium ion secondary battery. Graphitized MPCF gives high discharge capacity and good Ah efficiency. MPCF/Li cell shows an initial discharge capacity of 300 mAh/g and Ah efficiency above at a current density of 25 mA/g at V. Cylindrical lithium ion secondary battery was fabricated using mixed carbon anode and , cathode. In order to improve the cyclability of lithiun ion secondary battery, other carbons were added to the MPCF up to . The cycle performance of lithium ion secondary battery using mixed carbons was superior to those using graphitized MPCF.

High-capacity lithium-ion cells using graphitized mesophase-pitch-based carbon fiber anodes

We have developed high-capacity lithium-ion cells using graphitized mesophase-pitch-based carbon fiber (MCF) as an anode material. The graphitized MCF is a highly graphitized carbon fiber with a radial-like texture in the cross section. This structure contributes to the rapid diffusion of lithium ions inside the carbon fiber. The diffusion coefficient of lithium ions in the graphitized MCF was one order of magnitude larger than those for graphite, resulting in an excellent high-rate performance of the carbon electrode. The graphitized MCF anode showed larger capacity, a higher rate capability, and better reversibility than the graphite anode. The 863448 size (8.6 mm × 34 mm × 48 mm) prismatic cell with the graphitized MCF anode exhibited a large capacity of > 1000 mAh. At 3 A discharge, the prismatic cell had 95% of its capacity at 0.5 A discharge with a mid-discharge voltage of 3.35 V. The cell maintained > 85% of its initial capacity after 500 cycles and showed high capacity at −20 °C. It has thus been demonstrated that the prismatic cell using the graphitized MCF anode has excellent performance, and is an attractive choice for the power sources of cellular phones and other appliances.

Improved Carbon Anode Materials for Lithium-Ion Cells

ABSTRACTSeveral carbon materials have been studied for suitability as anode materials in lithium-ion cells. Carbons that have been included in this evaluation are three grades of commercially available mesophase carbon microbeads (MCMB) 6–28, 10–28 and 25–28, two specially prepared mesophase fibers (Amoco), a foreign mesophase fiber and KS-15 graphite (Lonza). Differences in cycling behavior between the three types of MCMB material are shown. Data of full lithium-ion cells demonstrate the effect that the choice of carbon material has on the cell discharge voltage and capacity. Lithium reference electrode experiments in full cells (3.0–4.0Ah capacity), elucidate the dynamics under several charge/discharge regimes and provide a comparison between the performance of carbon fiber and graphite anode materials. These test results indicate that the fibers can be charged at significantly higher rates than graphite without showing polarization at the anode. Full and half cell data also demonstrates the high coulombic efficiencies of the mesophase materials and first cycle efficiencies as compared to graphite. A comparison of two mesophase materials with different textures in full cells under strenuous cycling conditions shows significant differences in capacity retention. SEM photos of fibers showing the different textures are also presented.

ChemInform Abstract: Rechargeable Lithium‐Ion Cells Using Graphitized Mesophase‐Pitch‐Based Carbon Fiber Anodes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Rechargeable Lithium‐Ion Cells Using Graphitized Mesophase‐Pitch‐Based Carbon Fiber Anodes

The electrochemistry of lithium intercalation into a graphitized mesophase‐pitch‐based carbon fiber with a radial‐like texture used as the anode material in rechargeable lithium‐ion cells was characterized. The radial‐like texture in the cross section of the carbon fiber contributed to the rapid diffusion of lithium ions, resulting in the high rate capability. The anode performance of the graphitized carbon fiber was superior to that of the graphite. Experimental flat‐plate lithium‐ion cells using the graphitized carbon fiber anode exhibited a high mid‐discharge voltage of 3.7 V, a high rate capability, and a long cycle life of more than 400 cycles at 2 mA/cm2 during charge‐discharge cycling between 4.2 and 2.7 V. The long cycle life obtained for the cell was due to no significant change in resistance associated with the passivating films on the graphitized carbon fiber with extended cycles. It was also demonstrated that A size cells using the graphitized carbon fiber anode have excellent rate performance at discharge currents between 0.25 and 3 A, a large discharge capacity of 0.95 Ah, and a high energy density of 310 Wh/dm33 and 120 Wh/kg.

POSITION-SENSITIVE X-RAY DETECTOR SYSTEM FOR HIGH RESOLUTION PIXE MEASUREMENTS

A position-sensitive proportional counter with a carbon fiber anode, a goniometer and its associated electronics have been constructed to measure particle induced X-rays. The counter is easy to construct and its volume is about one order of magnitude smaller than a commercially available delay-line PSPC. This counter has good position linearity and uniform sensitivity distribution. Comparison is made between the new type of PSPC and an older one previously reported. It is shown that an enlargement of the X-ray window of the PSPC is effective for improving the detection efficiency.

APPLICATION OF A CHARGE-DIVISION, POSITION-SENSITIVE PROPORTIONAL COUNTER TO HIGH-RESOLUTION PIXE MEASUREMENTS

A charge-division, position-sensitive proportional counter with a carbon-fiber anode and its associated signal processor has been developed. This counter is very small in volume with a simple structure and vacuum proof. The spatial resolution of 0.36 mm was achieved under a gas pressure of 1.7×105 Pa. A correlation factor between the position and the channel number was measured to be 0.97, indicating good linearity of the system. The detector was combined with a crystal spectrometer in order to measure spectra of particle-induced characteristic X rays. Energy resolutions measured at Si Kα (1.74 keV) and Fe Kα (6.4 keV) X rays are 4 and 34 eV, respectively.

Electrochemical behaviour of polarised carbon fibre micro-electrodes

It has been shown previously that when a pair of glassy carbon electrodes are used in the electrolysis of a 0.5 M sodium sulphate solution, the anode is electrochemically attacked. In the work reported here, the behaviour of a pair of carbon fibre micro-electrodes was examined and it was found from chronopotentiometric graphs that the carbon fibre anode showed a similar behaviour to a glassy carbon anode. Scanning electron micrographs showed that electrolysis alters the surface of the carbon fibre anode whereas the cathode surface remains unchanged. The voltammetric curves obtained confirmed that the carbon fibre anode was markedly changed after electrolysis.

シンクロトロン放射光によるＸ線応力測定

In the field of X-ray stress measurement of polycrystalline materials, a diffraction plane at higher Bragg angle has to be selected in order to obtain the precise value of stress. However, the stress measurement on an optional (hkl) plane desired is not always possible because the X-ray beam exited from a metal target has a dispersive wave length.Recently, we have been able to use the synchrotron radiation source (SR) as an excellent X-ray source. In Japan, the facility of synchrotron radiation (Photon Factory, PF) was constructed in the National Laboratory for High Energy Physics (KEK) at Tsukuba academic city. The use of this SR enables the stress measurements on many (hkl) planes with high accuracy in the higher Bragg angle region by providing an X-ray beam having an optional wave length.We have started the X-ray stress analysis by use of the synchrotron radiation source. This paper reports the system of measurement and some results of preliminaly experiments.Since a monochromatic X-ray beam is required for the stress measurement, we used a beam line which consists of a double crystal monochrometer and a focusing mirror. X-rays between 4KeV (λ=0.31nm) and 10KeV (λ=0.12nm) are available with this optical system. We adopted a constant Bragg angle of 2θ=154° for all the diffraction planes. A PSPC having a carbon fiber anode is made and used as a detector with the use of a fast digital signal processor.We could observe the diffraction profiles from (200), (211), (220), (310) and (321) crystal plane of alpha iron, respectively, and the residual stresses in these planes except the (200) plane were measured with high accuracy in a short time.Such feature especially suits the stress analysis of the material which has preferred orientation or stress gradient.