All-solid-state electric double-layer capacitor with isotropic high-density graphite electrode and polyethylene oxide/LiClO₄ polymer electrolyte

An isotropic high-density graphite was used as a polarizable electrode of all-solid state electric double-layer capacitor using polyethylene oxide (PEO) or gel PEO electrolyte. The all-solid-state capacitor with high-density graphite electrodes possesses higher differential capacity than the other flat electrodes in PEO/LiClO₄ ([EO]/[Li⁺] = 8:1) solid polymer electrolyte at 80°C or PEO/PC/LiClO₄ ([EO]/[PC]/[Li⁺] = 8:8:1) gel electrolyte at ambient temperature. The capacitance of the electric double layer of the high-density graphite electrode was strongly influenced by the cell temperature and concentration of LiClO₄, because of the different state of the polymer crystallinity and different interface contact state between the high-density graphite electrode and the solid electrolyte. The all-solid-state capacitor with PEO/LiClO₄ ([EO]/[Li⁺] = 8:1) solid polymer electrolyte and PEO/PC/LiClO₄ ([EO]/[PC]/[Li⁺] = 8:8:1) gel electrolytes showed good charge/discharge behavior with a relatively high capacitance at 80 and 20°C, respectively.