High-voltage aqueous symmetric supercapacitors based on 3D bicontinuous, highly wrinkled, N-doped porous graphene-like ultrathin carbon sheets

Abstract

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.