Nickel sulfide and cobalt-containing carbon nanoparticles formed from ZIF-67@ZIF-8 as advanced electrode materials for high-performance asymmetric supercapacitors

As a typical pseudocapacitance material, NiS is considered a promising electrode material due to its high theoretical specific capacitance and abundant reserves. However, the electrical conductivity is poor, resulting in a decrease in cycle stability and rate performance. Here, we introduce cobalt-containing porous nanocarbon (Co-NC) derived from zeolite-imidazolate frameworks (ZIFs) as a supporting base to design a hybrid structure. As an electrode material, NiS@Co-NC nanocomposite has a composite effect of double-layer capacitive porous carbon and pseudo-capacitance NiS nanoparticles and excellent electrochemical performance. Specifically, the specific capacitance of NiS@Co-NC nanocomposite is as high as 1116.6 F.g(-1) when the current density is 1 A.g(-1), and capacity retention is 90.177% at a very high current density of 10 A.g(-1) after 5000 cycles. Moreover, the fabricated hybrid supercapacitor delivers an energy density of 21.6 Wh.kg(-1) at 799.9 W.kg(-1) with coulombic efficiency of 90.177%, and 14.22 Wh.kg(-1) at a high power density of 7999.9 W.kg(-1), along with excellent cyclic stability of 89.85% at 5 A.g(-1) after 5000 cycles. All results indicate that NiS@Co-NC nanocomposites have the potential to be applied as electrodes in hybrid supercapacitors and other energy storage devices.