Flower-like Cu1.8S nanostructures for high-performance flexible solid-state supercapacitors

Highlights: • Flower-like Cu_1.8S was synthesized from tris(thiourea)copper(I)chloride complex. • Flower-like Cu_1.8S with different petal morphology was prepared. • A flexible SSC decorated with 3D flower-like Cu_1.8S was prepared. • Flower-like Cu_1.8S SSC with thinner petal thickness showed high capacitance. In wearable and portable electronic devices, small size, light weight, flexibility, and easy operability are necessary for energy storage systems, such as battery and supercapacitor. To improve the performance, high specific capacity and high energy and power densities are also required. In this study, flower-like Cu_1.8S nanostructures are synthesized from a single source tris(thiourea)copper(I) chloride complex precursor. The different-sized Cu_1.8S nanostructures with flower-like petal morphology are successfully synthesized by addition of capping agents such as sodium dodecyl sulfate (SDS) and ethylenediaminetetraacetic acid (EDTA) with ethylene glycol (EG) as a solvent. The petal thicknesses vary from 60 to 30 nm, resulting in the increase in its specific surface area. The as-prepared nanostructures are tested for their supercapacitor performances in KOH electrolyte medium. The EDTA-Cu_1.8S electrode provides a high specific capacitance of 1050.0 F g⁻¹ as compared with SDS-Cu_1.8S (773.0 F g⁻¹) and EG-Cu_1.8S (625.4 F g⁻¹). Flexible solid-state symmetric supercapacitors are also fabricated from EDTA-Cu_1.8S which deliver a high volumetric capacitance (4.5 F cm⁻³) and energy density (0.5 mWh cm⁻³).