ZIF-67 derived in-situ grown N–Co3S4-GN/CNT interlinked conductive networks for high-performance especially cycling stable supercapacitors.

Transition metal sulfides (TMSs) have become promising candidates as electrode materials in energy storage fields thanks to the high theoretical capacity. However, their application is hindered by depressed electrical conductivity and poor cycling performance. Herein, we proposed a ZIF-67 derived, nitrogen-doped, graphene-coated and carbon nanotubes-interlinked 3D Co 3 S 4 /C conductive network (N–Co 3 S 4 -GN/CNT) for high-performance supercapacitors. Through controlling the mass ratio of ZIF-67, melamine and g-C 3 N 4 , various microstructures with determined electrochemical performance could be achieved. The nanocomposites synthesized with the ingredient mass ratio of 2: 1: 1 (NCSC-211) were proven to have the most excellent comprehensive electrochemical properties. In the NCSC-211 nanostructure, multi-layer graphene function as conductive shells for improved cycling performance by alleviating pulverization caused by volume change, thick CNTs act as conductive bridges and agglomeration spacers that increase electron conductivity and provide more active sites for redox reaction and doped-nitrogen offer enhanced wettability to electrolyte and faster electron transfer. The NCSC-211 electrode displayed specific capacitance of 1158 F g−1 at 1 A g−1, rate capability of 86% at 10 A g−1 and extraordinary cycling stability with 97.2% capacitive retention after 4000 cycles. Furthermore, the assembled asymmetric supercapacitor NCSC-211//activated carbon exhibited energy density of 43.73/37.69 Wh kg−1 at power density of 800/8000 W kg−1 and capacity retention of 95.3% after 5000 cycles at 5 A g−1. The designing strategy of in-situ grown instead of additional added conductive phase that fully-covered and strongly-interlinked network nanostructure may pave the road towards TMSs in synthesizing energy storage materials by compensating their intrinsic drawbacks. The N–Co 3 S 4 -GN/CNT 3D interlinked conductive network nanostructures were rationally designed and successfully synthesized as electrode materials for supercapacitors. The NCSC-211 electrode exhibited the most comprehensive electrochemical performance especially long cycle life, which thanks to the in-situ grown multi-layer graphene shells as well as thick carbon nanotubes bridges and spacers. [Display omitted] • Construction of N–Co 3 S 4 -GN-CNT 3D interlinked conductive network nanostructure. • The graphene and carbon nanotubes are in-situ grown instead of additional synthesized and further composited. • Tightly-coated graphene conductive shells restrain volume expansion of Co 3 S 4 nanoparticles. • Strongly-interlinked CNTs conductive bridges and agglomeration spacers increase electrical conductivity and active sites. • Extraordinary cycling stability with 97.2% capacitance retention after 4000 cycles for cobalt sulfide electrode materials. [ABSTRACT FROM AUTHOR]