Nickel Cobalt Sulfide Nanosheets on Cotton Fabric-Derived Carbon Substrates as Self-Standing Binder-Free Electrodes for Asymmetric All-Solid-State Supercapacitors

Cobalt nickel sulfide (Ni-Co-S), a typical bimetallic sulfide, is regarded as a promising electrode material for supercapacitors (SCs). In this study, the electrodeposition process is employed to grow vertically aligned Ni-Co-S nanosheets on a carbon film (CF) substrate derived from cotton fabrics. The conductive and porous CF film not only ensures the uniform distribution of Ni-Co-S nanosheets but also offers an efficient pathway for the transportation of electrons and electrolyte ions. The Ni-Co-S nanosheet arrays, characterized by their small thickness and open pores, facilitate to provide a rapid diffusion path for electrolyte ions and expose sufficient active surfaces for charge storage. The synergistic effect resulting from the rational combination of Ni-Co-S nanosheets and the CF film substrate endows the film electrode with a high areal capacitance of 1800 mF cm⁻² at 2 mV s⁻¹ and remarkable mechanical flexibility. Furthermore, when an all-solid-state asymmetric SC device is assembled, a high energy density of 324.1 mWh cm⁻² is achieved at a power density of 2252.4 mW cm⁻².