Electrochemical intercalation of tetraethylammonium tetrafluoroborate into KOH-treated carbon consisting of multi-graphene sheets for an electric double layer capacitor

Carbons produced by calcination at 700 similar to 850 degrees C, of the materials derived from petroleum cokes and pitches consist of well-grown graphite-like layers with an average inter-layer distance of d(infinity 2) = 0.35 similar to 0.365 nm. Additional heat treatment of the carbon with KOH at 800 degrees C can provide the expansion of inter-layer distance up to d(infinity 2) = 0.36 similar to 0.385 nm and the latent ability of electrochemical intercalation of Et4N+ and BF4- in PC into the multi-graphene layers. Using the KOH-treated carbons as electrodes of EDLC, a high-density energy store such as 25 similar to 30 F/cm(3) of dry total electrodes operating at 3.5 similar to 4.0 V is available when the depth of the cell is rigidly restricted.