Hydrothermally synthesized copper telluride nanoparticles: First approach to flexible solid-state symmetric supercapacitor

Supercapacitors, with their high-power density, rapid charge–discharge rates, and long cycle life, have emerged as promising energy storage devices for numerous applications. Among the various materials explored for supercapacitor electrodes, copper-based chalcogenides have gathered significant attention due to their intriguing electrochemical properties and simple synthesis routes. While there have been thorough investigations in other fields, only a limited number of studies have focused on the specific application of copper telluride nanoparticles as supercapacitors. In this study, we present a novel approach utilizing hydrothermally synthesized copper telluride (Cu_2-xTe) nanoparticles as binder-free electrodes on flexible stainless steel (SS) substrates. The Cu_2-xTe nanoparticles, with their small particle (38 nm) and highly crystalline structure, enhance charge storage and promotes a pseudocapacitive behavior, resulting in a high specific capacitance [381 F/g (163 mF/cm²) at 2 mV/s] in a 2 M KCl electrolyte solution. Moreover, we studied and explained the distinct contributions of surface-controlled and diffusion-limited processes to the overall charge storage capacity of the electrode. Our pioneering effort includes the fabrication and analysis of flexible, symmetric solid-state supercapacitor devices utilizing Cu_2-xTe electrodes with PVA-LiClO₄ gel electrolyte. These devices demonstrate an energy density of 11 Wh/kg, a power density of 800 W/kg, and an impressive 85 % retention of cyclic stability after 5000 cycles.