Porous nanosheet-nanosphere@nanosheet FeNi₂-LDH@FeNi₂S₄ core-shell heterostructures for asymmetric supercapacitors

Transition bimetallic sulphides have emerged as important electrode materials for supercapacitors owing to their low toxicity, environmental friendliness, cost-effectiveness, multiple oxidation states, high natural abundance, flexible structure, and high theoretical specific capacitance. Herein, a porous nanosheet-nanosphere@nanosheet FeNi₂-LDH@FeNi₂S₄ (FNLDH@FNS) core-shell heterostructure was directly prepared on nickel foam (NF) via a two-step hydrothermal method. The prepared electrode material exhibits an outstanding electrochemical performance. The specific capacity (C_s) values are 806 and 450 C g^-1 at current density (D_c) values of 1 and 6 A g^-1, respectively, revealing a satisfactory magnification performance. In addition, the FNLDH@FNS electrode exhibits a long cycle life with an supercapacitor (SC) retention rate of 92.3% after 5000 cycles at a D_c of 6 A g^-1. The FNLDH@FNS//activated carbon (AC) asymmetric SC assembled with FNLDH@FNS (positive electrode) and activated carbon (AC, negative electrode) displays an energy density (E_d) of 36.67 Wh kg^-1 and a power density (P_d) of 775.17 W kg^-1.