Two-dimensional hierarchical MoS2 lamella inserted in CoS2 flake as an advanced supercapacitor electrode

Abstract

The two-dimensional hierarchical structure has a positive effect on improving the stability of the electrode materials for supercapacitors. In this work, an exquisite hierarchical structure of CoS2 flake with the two-dimensional MoS2 lamella (MoS2@CoS2) was constructed using flake-like ZIF-67 as a precursor through multiple calcination and one-step sulfuration. The CoS2 nanosheets composed of CoS2 nanoparticles anchored on the carbon skeleton could provide a stable structure for subsequent reactions. Moreover, the inserted 2D cross-linked MoS2 multilayers could effectively prevent the interlayer expansion and structural collapse, and especially ensure the electrochemical performance and morphological stability of the transition metal sulfides. As a result, MoS2@CoS2 exhibits an extraordinary specific capacitance (950 F g−1 at 1 A g−1) and an appreciable cycle life with a capacitance retention of 94.6% (10, 000 cycles at 10 A g−1). Meanwhile, the MoS2@CoS2//reduced graphene oxide (RGO) asymmetric supercapacitor shows an energy density of 33.94 Wh kg−1 at a power density of 1040 W kg−1. Such excellent performance benefits from more electrochemically active sites and the rapid kinetics reaction which was ascribed to the rational design of two-dimensional hierarchical structure.