| 摘要 |
PROBLEM TO BE SOLVED: To provide a separator for electric double-layer capacitor that has superior mechanical strength, proper energy density, and low internal resistance. SOLUTION: This separator is obtained by introducing an oxygen-containing functional group into a fibrous sheet, containing thin polyester fibers having degree of fineness of <=0.45 dtex (decitex) in an amount of >=30 mass%; the separator has a thickness of 10-50μm; in addition, the difference between the ratio of the number (Oa) of oxygen atoms to the number (Ca) of carbon atoms on the surface of the fibrous sheet, before the functional group is introduced; and the ratio of the number (Ob) of oxygen atoms to the number (Cb) of carbon atoms on the surface of the sheet, after the functional group has been introduced, is adjusted to >=0.1, by measuring the number of oxygen and of carbon atoms through the means of X-ray photoelectron spectroscope.
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