High-Performance Asymmetric Supercapacitor Designed with a Novel NiSe@MoSe2 Nanosheet Array and Nitrogen-Doped Carbon Nanosheet

Herein, a novel asymmetric supercapacitor (ASC) with high energy density is fabricated based on the NiSe@MoSe2 nanosheet arrays and the nitrogen-doped pomelo mesocarps-based carbon nanosheet (N-PMCN) as a positive electrode and a negative electrode, respectively. The novel NiSe@MoSe2 nanosheet arrays are designed and prepared by a facile one-step hydrothermal growth method from nickel foam as a nickel precursor and nucleation framework. The N-PMCN is prepared using simultaneous CaCl2 activation and urea nitrogen-doped processes from thepomelo mesocarps as a biomass-based carbon precursor. Because of the unique nanosheet array architecture of NiSe@MoSe2 and interconnected sheet-like porous morphology with high nitrogen content (∼9 wt %) of N-PMCN, they exhibit a maximum specific capacity of 128.2 mAh g–1 and high specific capacitance of 223 F g–1 at a current density of 1 A g–1. Moreover, the assembled novel NiSe@MoSe2//N-PMCN ASC device with a maximum operating voltage of 1.65 V has demonstrated a high energy density of 32.6 Wh kg–1 at a power density of 415 W kg–1 and outstanding cycling stability with 91.4% capacitance retention after 5000 cycles in aqueous electrolyte.