A novel thin, wood-based carbon material with heterogeneous pores, film of lignocellulosic carbon material (FLCM), was successfully fabricated by carbonizing softwood samples of Picea jezoensis (Jezo spruce). Simultaneous increase in the specific surface area of FLCM and its affinity for electrolyte solvents in an electric double-layer capacitor (EDLC) were achieved by the vacuum ultraviolet/ozone (VUV/O3) treatment. This treatment increased the specific surface area of FLCM by 50% over that of original FLCM. The results obtained in this study confirmed that FLCM is an appropriate self-supporting EDLC electrode material without any warps and cracks

Flat lignocellulosic carbon materials (FLCMs) with a honeycomb structure were successfully fabricated by carbonizing the softwood Picea jezoensis (Ezomatsu, Japanese conifer) and the hardwood Cercidiphyllum japonicum (Katsura). Scanning electron microscopy images of the FLCMs showed distinct differences in the tracheid diameter distributions between the FLCMs made from the softwood and hardwood. High-temperature heating decreased the electrical resistivity of the FLCMs. Vacuum ultraviolet irradiation in an oxygen atmosphere (VUV/O3) helped in increasing the surface hydrophilicity and specific surface area of the materials while maintaining their low electrical resistivity. The surface-treated FLCMs were successfully used to fabricate self-supporting electrodes for electric double-layer capacitors (EDLCs).

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A novel flat, wood-based carbon material with heterogeneous pores, referred to as flat lignocellulosic carbon material (FLCM), was successfully fabricated by carbonizing samples of the softwood Picea jezoensis (Ezomatsu or Jezo spruce, a Japanese conifer). Simultaneous improvements of the specific surface area of the FLCM and the affinity of electric double-layer capacitor (EDLC) for electrolyte solvents were achieved by vacuum ultraviolet/ozone (VUV/O 3 ) treatment. The specific surface area of the VUV/O 3 -treated FLCM showed a 50% increase over that of the original FLCM. The spectra measured by X-ray photoelectron spectroscopy (XPS) indicated that the number of O-C=O (carboxyl or ester) bonds increased, whereas the number of C-C bonds decreased. Additionally, the feasibility of using the FLCM as a self-supporting electrode in EDLCs was examined by measuring the electrochemical properties in a threeelectrode system. The FLCM was confirmed as an appropriate self-supporting EDLC electrode material without warps and cracks. In addition, the FLCM can be used without any binder. Realization of FLCM-based EDLC electrodes with bendability, an area of several tens of square centimeters, and no risk of warp or crack formation, were indicated. Thus, FLCMs present a fascinating class of self-supporting carbon electrode materials for EDLCs.