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In this study, a facile pyrolysis process is utilized to convert a mantis shrimp shell into a 3D bicontinuous porous, highly wrinkled, nitrogen-doped, graphene-like ultrathin carbon sheet (3D BWGC). The 3D BWGC achieves a high surface area of 2300 m2 g−1 and a pore volume of up to 1.63 cm3 g−1. The specific capacitance of the 3D BWGC in 0.5 M H2SO4 electrolyte is 370.9 F g−1 at a current density of 1 A g−1 and an operating voltage window of 1.1 V. By introducing Fe2+, the operating voltage window of 3D BWGC symmetric supercapacitors can reach 1.8 V in a neutral electrolyte, and a specific capacitance of 317.2 F g−1 can be obtained at a current density of 0.5 A g−1. Remarkably, the fabricated symmetric supercapacitors using 2 M MgSO4 + 0.05 M FeSO4 electrolyte demonstrated an energy density as high as 17.7 W h kg−1 at a power density of 180 W kg−1. The assembled supercapacitors exhibit good cycling performance, maintaining an initial capacitance of 87.2% over 30 000 cycles. These excellent performances indicate the promising prospects of 3D BWGC in high-performance electrochemical energy storage. [ABSTRACT FROM AUTHOR]

Interconnected hierarchical porous carbon was successfully prepared by direct carbonization of industrial waste sodium lignosulfonate without additional templating and activation agents. The as-prepared carbon sample shows a moderate specific surface area of 903 m2 g−1 and high contents of 8.11 at% oxygen and 1.76 at% nitrogen, which could improve the electrolyte-affinitive surface area in an aqueous electrolyte. When used as electrode materials for symmetric supercapacitors in 7 M KOH electrolytes, the as-synthesized carbon sample exhibits a significantly high gravimetric capacitance of 247 F g−1, a volumetric capacitance of 240 F cm−3, and an areal capacitance of 27.4 μF cm−2 at a current density of 0.05 A g−1. Moreover, a superior energy density of 8.4 W h L−1 (at 13.9 W L−1) and a power density of 5573.1 W L−1 (at 3.5 W h L−1), as well as a remarkable cycling stability after 20 000 cycles at two different current densities were achieved for the assembled supercapacitors. [ABSTRACT FROM AUTHOR]