Rational Design of Porous Structured Nickel Manganese Sulfides Hexagonal Sheets-in-Cage Structures as an Advanced Electrode Material for High-Performance Electrochemical Capacitors

The design of hierarchical electrodes comprising multiple components with a high electrical conductivity and a large specific surface area has been recognized as a feasible strategy to remarkably boost pseudocapacitors. Herein, we delineate hexagonal sheets-in-cage shaped nickel-manganese sulfides (Ni-Mn-S) with nanosized open spaces for supercapacitor applications to realize faster redox reactions and a lower charge-transfer resistance with a markedly enhanced specific capacitance. The hybrid was facilely prepared through a two-step hydrothermal method. Benefiting from the synergistic effect between Ni and Mn active sites with the improvement of both ionic and electric conductivity, the resulting Ni-Mn-S hybrid displays a high specific capacitance of 1664 F g^-1 at a current density of 1 A g^-1 and a capacitance of 785 F g^-1 is maintained at a current density of 50 A g^-1 , revealing an outstanding capacity and rate performance. The asymmetric supercapacitor device assembled with the Ni-Mn-S hexagonal sheets-in-cage as the positive electrode delivers a maximum energy density of 40.4 Wh kg^-1 at a power density of 750 W kg^-1 . Impressively, the cycling retention of the as-fabricated device after 10 000 cycles at a current density of 10 A g^-1 reaches 85.5 %. Thus, this hybrid with superior capacitive performance holds great potential as an effective charge-storage material.