Composite electrode materials based on nickel cobalt sulfide/carbon nanotubes to enhance the Redox activity for high performance Asymmetric supercapacitor devices

Asymmetric supercapacitor or supercapattery, is a unique device that combines the best features of both supercapacitors and batteries. Specifically, it offers improved cycle life and specific power, which are the strengths of supercapacitors, along with the high energy density that batteries are known for. This technology represents a significant advancement in energy storage and has the potential to revolutionize various industries. In this work, nickel cobalt sulfide (NiCoS) was synthesized through a hydrothermal process and then physically mixed with carbon nanotubes (CNTs). The electrical characteristics of the material were analyzed using a three-electrode and a two-electrode setup. In a three-electrode system, NiCoS/CNTs composite showed a specific capacity of 1542.1 Cg-1 at 2.5 Ag-1. In an asymmetric device, the negative and positive electrode was activated carbon (AC) and NiCoS/CNTs, respectively. The composite of NiCoS/CNTs exhibited a specific capacity of 161.3 Cg-1, which is noteworthy. Additionally, the material demonstrated an exceptional energy density of 35.5 Whkg-1 and a power density of 1800 Wkg-1. The capacity retention of the composite material was 84.0% after 5000 cycles. The composite electrode materials of transition metal sulfide and CNT in a 90/10 wt. ratio provides an opportunity to develop high-performance energy storage devices.