Construction of hierarchical zinc cobalt sulfide@nickel sulfide core-shell nanosheet arrays for high-performance asymmetric solid-state supercapacitors

Abstract

To fulfill the promise of high-performance supercapacitors (SCs) with a high specific capacitance, superior rate capability, long cycling life, and high energy density, it is desirable to rationally construct core-shell composite electrode materials with tailored architectures and components. In this reported study, hierarchical Zn0.76Co0.24S@Ni3S2 core-shell nanosheet arrays (CSNAs) on Ni foam are designed and synthesized, in which interconnected Zn0.76Co0.24S nanosheet cores are initially constructed through a hydrothermal reaction combined with a sulfurization process. These nanosheet cores are then uniformly wrapped by a Ni3S2 nanosheet shell using an electrochemical deposition reaction. The hierarchical structure of nanosheets@nanosheets together with the synergistic effect between the Zn0.76Co0.24S and Ni3S2 components, enables the composite electrode to exhibit a large specific capacity (1209 C g−1 at 2 A g−1), good rate capability (78.6% capacity retention at 20 A g−1), and remarkable cycle stability (94.9 capacity retention after 5000 cycles at 20 A g−1). Furthermore, the fabricated Zn0.76Co0.24S@Ni3S2//active carbon (AC) asymmetric solid-state supercapacitor cell (ASSC) can deliver a high energy density of 53.8 W h kg−1 at a power density of 853 W kg−1. These results showcase the great application potential of the novel core-shell composite electrode in high-performance SCs, and they also provide an alternative method for constructing metal sulfide-based composite electrodes with optimum electrochemical performance.