Ultralong and Millimeter-Thick Graphene Oxide Supercapacitors with High Volumetric Capacitance

The fabrication of a high energy density supercapacitor with electrodes bearing ultrahigh aspect ratio active materials is still a big challenge. Here, we successfully developed ultralong and millimeter-thick supercapacitors, which enable practical applications due to the large electrochemical volumetric capacitance overcoming the limits of previous carbon-based materials. The gel graphene oxide fibers (GOFs) with an ultrahigh aspect ratio of over 20,000,000 were completely reduced at room temperature and biscrolled with a conductive Korean traditional paper used as the matrix material for the supercapacitors without any post-treatment. The average cell capacitance value of the yarn-type supercapacitors containing 80 reduced GOFs is maximized at a scan rate of 100 mV/s. The capacitance measured at a scan rate of 1000 mV/s is over 75% of that measured at 100 mV/s.