Hierarchical Porous Graphene Carbon-Based Supercapacitors

Abstract

A high-rate\ngraphene-based supercapacitor is very attractive for\nthe practical application of graphene. Here, we first synthesized\nthe films of the hybrids of biomass cellulose and large literal sheet\nsizes and weakly defective graphene flakes reaching high thermal conductivity\nand then converted them into hierarchical porous graphene carbon materials\nreaching superior supercapacity. The interconnected porous carbon\nframework, with macroporous walls sandwiched by micro/mesoporous activated\ncarbon covering graphene flakes, was synthesized by template-free\nlow-temperature activation of the cellulose/graphene hybrids at 650\n°C. The graphene flakes could probably assist both the decrease\nin the temperature of the chemical activation of cellulose and the\nformation of the hierarchical carbon pores without destroying their\nsp² bonds. The porous graphene carbon-based supercapacitors\nexhibit a reversible specific capacitance of ∼300 F/g and ultrahigh\nenergy storage performance of 67 Wh/kg, 54 Wh/L, and 60 kW/kg over\na 45 s discharge time.