Self-standing and macroporous carbon materials were prepared by using silica opals ͑colloidal crystal͒ as a template. Poly͑furfuryl alcohol͒ was synthesized in the interstice of the silica colloidal crystals, followed by carbonization at 1000°C. The silica templates were etched off to give inverse opal carbons. The inverse opal carbons were characterized by scanning electron micrograph ͑SEM͒, reflection spectroscopy, elemental analysis, infrared spectroscopy, X-ray diffraction, direct current conductivity, and N 2 -adsorption/desorption experiments. The SEM images and the reflection spectra indicated periodic porous structures that were negative structures of the silica opal templates. The inverse opal carbons were hard carbons, mainly consisting of amorphous incompletely graphitized structures, and have electronic conductivity of 10 2 S cm −1 . The nitrogen adosorption/desorption experiments clarified that the carbons have large N 2 -BET ͑Brunauer-Emmett-Teller͒ specific surface area resulting from a lot of mesopores, in addition to macropores based on the silica templates. Electric double-layer charging and discharging of the carbons were studied in a tetraethylammonium tetrafluoroborate/propylene carbonate solution. The electric double-layer gravimetric capacitance and the coulombic efficiency of the inverse opal carbon electrodes in the solution increased with a decrease in the diameter of the silica spheres used for the opal templates and became superior to those of a typical activated carbon.The design and fabrication of the electrode/electrolyte interfaces, up to the nanometer level in order to increase the electron transfer rates and electric double-layer capacitance, are fascinating domains of current research in electrochemical energy conversion systems. 1,2 In the electrochemical systems, the interface needs to be fabricated so as to form cocontinuous phases of the electrode ͑electron-conducting͒ and electrolyte ͑ion-conducting͒ materials with a large contact area. Much interest in nanostructured materials has also stimulated the availability of nanostructured electrodes. Examples are seen in the fabrication of nanostructured electrodes and estimation of their electrochemical properties in various electrochemical systems. [3][4][5][6][7][8][9] Opal materials, which comprise a close-packed colloidal crystal of monodispersed spheres, have attracted much attention because of their photonic bandgap structure. 10-16 There also have been a number of studies on inverse opal materials fabricated by using the opal materials as a template. 17-31 Many research groups have suggested their applications, for example, to photonic crystal, catalysis, sensing, and separations, because the inverse opal structure itself possesses not only a three-dimensionally periodic structure but also large surface area per unit volume. Yan et al. 19 and Blanford et al. 20 referred to this class of three-dimensionally ordered macroporous materials as "3DOM" material.Recently, the inverse opal materials have been applied to electroch...

To design polymer electrolytes with high ionic conductivity as well as fast charge-transfer reaction at the electrode interface, electrolyte properties of a novel lithium salt of a weakly coordinating anion, lithium tetra(1,1,1,3,3,3-hexafluoro-2-propyl)aluminate, LiAl[OCH(CF 3 ) 2 ] 4 , have been studied in the bulk, in aprotic solvents, and in a polyether. Although the lithium salt melts at fairly low temperature, it shows poor conductivity even in the molten state because of its strong ionic association. However, in aprotic solvents, LiAl[OCH-(CF 3 ) 2 ] 4 exhibits a relatively high degree of dissociation because of weak coordination ability of the anion toward the cation. This is reflected in the higher ionic conductivity than that of common lithium salts, LiN-(SO 2 CF 3 ) 2 and LiBF 4 , at an identical concentration in the low polar solvents. In a polyether, an increase in the glass-transition temperature (T g ) of the polymer electrolytes with salt concentration is less marked in the LiAl[OCH(CF 3 ) 2 ] 4 system. The lithium salt can be incorporated in the matrix polyether at high concentrations without a loss in the ionic conductivity. The interface between the polyether electrolyte containing LiAl-[OCH(CF 3 ) 2 ] 4 and a metallic lithium electrode is statically stable for a long time, and the charge-transfer resistance decreases with increased salt concentration. These results indicate that an increase in LiAl[OCH-(CF 3 ) 2 ] 4 concentration in the polyether facilitates not only an increase in the ionic conductivity but also a decrease in the interfacial resistance.