Formation of nickel–cobalt sulphide@graphene composites with enhanced electrochemical capacitive properties

Abstract

Here, nickel–cobalt sulphide particles embedded in graphene layers (porous Ni–Co–S@G), were successfully prepared by one-step annealing of metallocene/metal–organic framework (MOF) hybrids involving simultaneous carbonization and sulfidation. Benefiting from the porous structure, highly conductive graphene layers and large loading of super-capacitive Ni–Co–S, the obtained Ni–Co–S@G composites exhibited excellent electrochemical performance with a specific capacitance of 1463 F g⁻¹ at a current density of 1 A g⁻¹. A flexible solid-state asymmetric supercapacitor (ASC), assembled with Ni–Co–S@G and active carbon, demonstrated a high energy density of 51.0 W h kg⁻¹ at a power density of 650.3 W kg⁻¹. It is noteworthy that the ASC offered robust flexibility and excellent performance that was maintained when the devices were bent at various angles. The results indicate that the as-prepared materials could potentially be applied in high-performance electrochemical capacitors.