NOVELTY - The composition has ketjen black subjected to hydrophilization treatment. A surface of a ketjen black powder is subjected to hydrophilization treatment to use the ketjen black having high electric conductivity as a conducting agent of an electrode using a water-based solvent. Cathode and anode are prepared by coating the composition on a cathode current collector and an anode current collector in a predetermined thickness. A mixture of an electrode active material, the conducting agent, and solvent is molded in a sheet shape by using a binder resin.    USE - Electrode active material composition for an electrochemical capacitor (claimed) i.e. electric double-layer capacitor or lithium ion battery, for portable electronic application such as notebook, cellular phone and personal digital assistant (PDA), for wind power generation application, hybrid electric vehicle, and for electric vehicle. Can also be used for super capacitor, ultra capacitor, pseudo capacitor, redo capacitor and hybrid capacitor.    ADVANTAGE - The composition attaches hydrophilic group on a surface of the ketjen black conducting powder having very strong hydrophobicity through the hydrophilic treatment, so that dispersibility of the active material of a carbon material such as activated carbon and the conducting agent can be improved when the electrode using a water-based solvent is prepared, thus preparing the electrode having improved flowability and uniformity of electrode active material slurry. The composition is designed such that the carbon material is homogeneously mixed in electrode active material slurry containing a water-based solvent as a base when the ketjen black subjected to hydrophilization treatment is used as the conducting agent, thus minimizing resistance of the electrode.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for an electrochemical capacitor. The composition comprises an electrode active material, which is a carbon material selected from a group consisting of activated carbon, carbon nanotube (CNT), graphite, carbon aerogel, polyacrylonitrile (PAN), carbon nanofiber (CNF), activated carbon nanofiber (ACKF), vapor grown carbon fiber (VGCF), and graphene.