ExperimentalMaterials: Aniline monomer (Beijing Chem. Co.) was distilled under reduced pressure. APS, H 3 PO 4 as the dopant, and other reagents were purchased from the Beijing Chemical Co. and used as received without further treatment. Octahedral cuprous oxide (Cu 2 O) crystals were prepared by a literature procedure [28].Polymerization: Aniline monomer (0.2 mL), sodium dodecylbenzenesulfonate (3.3 mg), and a quantitative amount of octahedral Cu 2 O crystals were mixed with H 3 PO 4 (0.06 mL), and the mixture was dissolved in 20 mL of deionized water under supersonic stirring. Stirring was continued for 10 min to form an emulsion of aniline/ H 3 PO 4 complex containing Cu 2 O particles at 0-5°C. The mixture was cooled in an ice bath, and 10 mL of a precooled aqueous solution of APS (0.46 g) was added. The reaction was magnetically stirred for 12 h in the ice bath. The resulting precipitate was washed several times with water, methanol, and ether, consecutively. Finally, the product was dried under vacuum at room temperature for 24 h.Characterization: Morphologies of the products were investigated with a JEOL JSM-6700F field-emission scanning electron microscope and a JEOL JEM-2010 transmission electron microscope. During the SEM investigation, the EDXS analysis was recorded with a LINK ISIS300 instrument. Infrared spectra in the range 400-4000 cm -1 on sample pellets made with KBr were measured by means of an infrared spectrophotometer (Bruker Tensor 27). The X-ray scattering of the products was carried out on an XRD instrument (Micscience M-18XHF with Cu Ka radiation). A digital multimeter (Keithley 196 System DMM) and a programmable direct-current voltage/current generator (Advantest R1642), as the current source were used to measure the electrical conductivity of compressed pellets at room temperature using a standard four-probe method. Recently, lithium-ion batteries have attracted much attention due to their potential applications in hybrid electric vehicles (HEVs). Several requirements such as high-rate performance, long life, safety, etc., are essential for the practical use of lithium-ion batteries in HEVs. Our research efforts have focused on enhancing the rate performance of lithiumion batteries. [1][2][3][4][5] Our initial efforts were focused on the charge-transfer resistance at the interface between the elec-COMMUNICATIONS
Surface
treatments are often applied to carbon materials to impart
specific functions to the surface. Surface oxidation is a typical
treatment to form oxygen-containing surface functional groups on carbon
fiber electrodes of redox flow batteries in order to enhance the performance,
which has attracted much attention as a large-scale electric energy
storage system. At present, however, little attention has been paid
to the effect of the edge plane exposure. In this study, fine etching
of the graphitized carbon fiber surface was attained by coating the
surface with a metal-containing carbonaceous thin film and thermal
oxidation. The etching was caused by the catalysis of the metal species;
the mechanism and the effect of the carbonaceous film were demonstrated
by in situ X-ray absorption fine structure measurements. The finely
etched surface possessed substantially enriched edge planes and an
enhanced activity for the positive and negative electrode reactions
of the vanadium redox flow battery. The flow cell test with the carbon
fiber electrodes after the tuned etching showed a significant decrease
in the overpotential and increase in the efficiency as well as stable
cycling performance.
The electrochemical properties of graphitized carbon nanospheres as a promising negative electrode material for high-rate lithium-ion batteries were correlated with lithium-ion intercalation and deintercalation behaviors.
For the development of high energy density lithium-ion batteries with the high rate performance, the enhancement of the ion transport in the electrolyte solutions impregnated in the porous electrodes is a key. To study the ion transport in porous electrodes, anodic nanoporous alumina (APA) self-standing membranes with macro-or meso-pores were used as model porous materials. These membranes had nearly spherical pore channels of discrete 20-68 nm in diameters. By using the geometric shape of the pores, we attempted to evaluate the specific ion conductivities of the organic electrolyte solution dissolving lithium salt simply. AC impedance spectroscopy measurement of a four-electrode cell with membranes showed one depressed semicircle in the Nyquist plots and this semicircle can be assigned as the ion transport resistance in the pores. The specific ion conductivities evaluated from the ion transport resistances and the geometric parameters showed very small values, even in the macro-pores, as compared with that of the bulk electrolyte solution.
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