Fabrication of hierarchical Zn–Ni–Co–S nanowire arrays and graphitic carbon nitride/graphene for solid-state asymmetric supercapacitors

The rational design and subsequent growth of apposite nanostructured transition metal sulfide on conductive scaffold with auspicious morphology to produce an advanced electrode material for supercapacitors is highly desirable to boost the electrochemical performance. Herein, a simplistic two-step strategy is designed to grow 3D-networked and mesoporous Zn–Ni–Co–S nanowire-like arrays (NWAs) on a Ni-foam scaffold, which includes the hydrothermal growth of Zn–Ni–Co-based hydroxyl precursor, followed by an effective sulfidation process. When employed as a free-standing electrode for supercapacitors, Zn–Ni–Co–S NWAs electrode delivers a superb capacity of 418.2 mA h g⁻¹ at 4.6 mA cm⁻², good rate capability (233.3 mA h g⁻¹ at 50 mA cm⁻²), and long cycle life (~89% of capacity retained after 10,000 cycles). Furthermore, a solid-state asymmetric supercapacitor device was constructed based on Zn–Ni–Co-S NWAs as cathode and graphitic carbon nitride/graphene as anode materials, achieves a cell capacity of 110.7 mA h g⁻¹ at 5 mA cm⁻², superior capacity retention (54% at 75 mA cm⁻²) and superb cyclic performance (93% after 10,000 cycles). The device delivers a superb energy density of 88.6 W h kg⁻¹ at a power density of 419.4 W kg⁻¹, and upholds an energy density of 47.6 W h kg⁻¹ at a high power density of 7048.4 W kg⁻¹.