Carbon material for electric double layer capacitor electrodes

Abstract

A carbon material for electric double layer capacitor electrodes which is obtained by a heat treatment and an activation treatment of a material pitch having a softening point in a range of 150 to 350° C., a ratio of amounts by atom of hydrogen to carbon (H/C) in a range of 0.50 to 0.90 and a content of optically anisotropic components of 50% or greater. The material pitch is preferably a synthetic pitch obtained by polymerizing a condensed polycyclic hydrocarbon such as naphthalene, methylnaphthalene, anthracene, phenanthrene, acenaphthene, acenaphthylene and pyrene in the presence of an ultra-strong acid catalyst such as a hydrogen fluoride-boron trifluoride complex. Electric double layer capacitors having a high electrode density and a high electrostatic capacity per unit volume can be constructed using the carbon material.

What is claimed is:  
     
         1 . A carbon material for electric double layer capacitor electrodes which is obtained by a heat treatment and an activation treatment of a material pitch having a softening point in a range of 150 to 350° C., a ratio of amounts by atom of hydrogen to carbon (H/C) in a range of 0.50 to 0.90 and a content of optically anisotropic components of 50% or greater.  
     
     
         2 . A carbon material for electric double layer capacitor electrodes according to  claim 1 , wherein the material pitch is obtained by polymerizing a condensed polycyclic hydrocarbon or a substance containing the condensed polycyclic hydrocarbon in a presence of a hydrogen fluoride-boron trifluoride complex.  
     
     
         3 . A carbon material for electric double layer capacitor electrodes according to  claim 1 , wherein the heat treatment comprises heating the material pitch at 400 to 800° C. under an atmosphere of an inert gas.  
     
     
         4 . A carbon material for electric double layer capacitor electrodes according to  claim 1 , wherein the heat treatment comprises placing a granular or powdery pitch obtained by a heat treatment into a reactor heated at 400 to 800° C., adding the material pitch to the pitch placed in the reactor under stirring and conducting the heat treatment.  
     
     
         5 . A carbon material for electric double layer capacitor electrodes according to  claim 1 , wherein the activation treatment comprises mixing the material pitch which has been subjected to the heat treatment with an alkali metal compound in an amount of 1 to 4 parts by weight per 1 part by weight of the material pitch and heating an obtained mixture at 400 to 900° C. under a stream of an inert gas.