Development of Electrode for Super Capacitor by Using Carbon Gels with Hieratically Controlled Porous Structure

通过间苯二酚与甲醛的溶胶-凝胶聚合、冷冻干燥和热解，合成了有趣的多孔炭材料，称为碳冷冻胶。冷冻机由碳纳米颗粒组成，颗粒之间形成中孔。碳冷冻是一种具有高比表面积和大介孔体积的独特材料，有望用作催化剂、吸附剂、双电层电容器、锂离子电池和层析分离材料。在本工作中，在不使用粘结剂的情况下，制备了用于双电层电容器系统的片状碳冷冻电极。以40M KOH为电解液，以Ag/AgCl3为参比电极的三电极电池进行了电容测量。结果表明，在1000℃条件下，通过对孔结构的精确控制和CO_2的活化，可以提高单位碳电极的电容。然而，这些方法并不能提高单位电极体积的电容。人们试图通过将间苯二酚和甲醛在有机冰箱的大中孔和大孔中重新聚合来提高碳冰箱电极的表观密度。结果表明，电极密度可提高一倍。对合成的片状碳冷冻电极的循环特性进行了实验研究。在有机冰箱中进行重聚合，可以使碳电极的容量增加一倍。即使重复充放电10000次，电容的降幅也在3%以内。通过循环伏安测试发现，所制备的碳电极的充放电是可逆的。

Interesting porous carbon materials, called carbon cryogels, have been synthesized via sol-gel polymerization of resorcinol with formaldehyde, freeze drying, and pyrolysis. The cryogel consists of nanoparticles of carbon, and mesopores are formed among the particles. Carbon cryogels are unique materials with high surface areas and large mesopore volumes, being expected to be used as catalysts, adsorbents, electric double layer capacitors, lithium ion battery, and materials for chromatographic separation.Monolithic carbon cryogels can be synthesized by molding the hydrogels prior to drying. In the present work, carbon cryogel electrodes in the form of tablet were prepared without using a binder for electric double layer capacitor systems. A three-electrode cell with an Ag/AgCl reference electrode whereby 40 M KOH was served as an electrolyte was performed to measure the capacitance. It was found that capacitance per carbon electrode weight could be increased based on precise controlling of porous structure and CO_2 activation at 1000℃. However, the capacitance per electrode volume could not be improved by these methodologies.The apparent density of carbon cryogel electrode was tried to be increased by repolymerizing resorcinol and formaldehyde in the large mesopores and macropores of organic cryogels, precursors of carbon cryogels. As the results, the density of electrode could be doubled. Cyclic characteristics of tablet-type carbon cryogel electrode synthesized were experimentally studied. The capacitance of carbon electrode could be doubled by the repolymerization in organic cryogels. The decrease of capacitance was within 3 %, even if the charging/discharging were repeated 10000 times. It was found that charging/discharging using the carbon electrode prepared were reversible by cyclic voltammetry.