Electric Double-Layer Capacitors Using
HClO4-Doped Silica Gels as a Solid Electrolyte
Atsunori Matsuda, Hiroshi Honjo, Masahiro Tatsumisago and Tsutomu Minami
Department of Applied Materials Science, Osaka Prefecture University,
Sakai, Osaka 599, Japan
Abstract. Electric double-layer capacitors were fabricated using polyvinyl alcohol-containing silica gels doped with
HClO4 as an electrolyte and activated carbon powders, ACP, hybridized with the silica gels as a polarizable electrode.
One of the capacitors fabricated had capacitance of 44 F/(gram of total ACP in the capacitor) at room temperature. The
large capacitance of the totally solid state electric double-layer capacitors fabricated is ascribed to the high proton
conductivity of the gels and the homogeneous hybridization of ACP with the gels by the sol-gel process.
A number of studies of solid-state materials that exhibit high proton conductivities have been
done for their application to a variety of electrochemical devices [1-4]. Inorganic gels prepared by
the sol-gel method are one of the most promising host materials to design high proton-conducting
composites because they contain a large number of micropores and mesopores filled with liquid
which can be utilized for fast proton transport [5-8]. We have developed the bulk silica gels and
silica gel films containing several kinds of acids and salts by the sol-gel method and found that the
conductivities of the silica gels containing perchloric acids and heteropoly acids are as high as 10-2 S
cm-1 at room temperature [5,9-11]. We have also succeeded in the application of the gels containing
prechloric acids to electrochromic devices using WO3 as a coloration material .
Electric double-layer capacitors have widely been used as a memory back-up device. Such
capacitors are composed of a pair of polarizable electrodes and an electrolyte. Activated carbons,
which exhibit large specific surface area and high electrical conductivities, have been used as a
polarizable electrode of