A waste utilization strategy for preparing high-performance supercapacitor electrodes with sea urchin-like structure

Three-dimensional (3D) porous nanomaterials are promising candidate for supercapacitor electrodes owing to their rich specific surface area and rapid electron transport rates. Herein, we report a simple mixed solvent-thermal process and one-step carbonization for the controllable synthesis of 3D hierarchically porous nanomaterials with a diverse porous microstructure consisting of nickel cobaltate, graphene, and polyurethane foam (PGNC). Significantly, PGNC exhibits a sea urchin 3D porous structure, which originates from the synergetic effect of hierarchical, interconnected pore structure with a distinctive unit structure composed of polyols and isocyanates, abundant amount of doped N atoms and surface opened channels with proper degree of graphitization, displays extraordinary electrochemical performances such as an ultrahigh reversible specific capacity of ca.1900 F·g−1 at a current density of 1.0 A·g−1 and excellent cycling stability (ca. 83% capacitance retention after 5000 charge/discharge cycles). Moreover, an asymmetric supercapacitor based on PGNC as positive electrode and the mixture of activated carbon with graphite as negative electrode manifested a high energy density of ca.52 Wh·kg−1 at a power density of 375 W·kg−1 in 6 M KOH aqueous electrolyte. Even at a higher power density of 3750 W·kg−1, the energy density can still reach 26 Wh·kg−1.