Flexible full-solid state supercapacitors based on zinc sulfide spheres growing on carbon textile with superior charge storage

Abstract

Nowadays, it is essential for us to design and fabricate efficient and cost-effective electrode materials for energy conversion and storage systems. Nanostructures are remarkable electrode materials due to their high surface area and large number of active sites. Herein zinc sulfide (ZnS) nanospheres with large surface area are hydrothermally grown on a flexible carbon textile (CT). The specific area and porosity are analyzed in detail under different pressures. The electrode based on the ZnS assembled CT (ZnS-CT) exhibits a high capacitance of 747 F g⁻¹ at a scan rate of 5 mV s⁻¹ in the LiCl aqueous electrolyte. The ZnS-CT is directly used as the binder free electrode for the fabrication of the symmetric flexible full solid state supercapacitor. The ZnS-CT supercapacitor shows excellent electrochemical performance along with light weight, thinness and good flexibility. The ZnS-CT supercapacitor demonstrates good capacitive behavior with a high specific capacitance of 540 F g⁻¹ (areal capacitance of 56.25 F cm⁻²) at a scan rate of 5 mV s⁻¹ with good rate capability and excellent cycling stability (94.6% retention of initial capacitance after 5000 cycles) at a constant current density of 0.8 mA cm⁻². A high energy density of 51 W h kg⁻¹ at a power density of 205 W kg⁻¹ is achieved, indicating excellent ion accessibility and charge storage ability. Furthermore, three charged supercapacitors connected in series can light 4 red color light emitting diodes (2.0 V, 15 mA) for 2 min. ZnS nanospheres with large specific surface area combined with flexible carbon textile substrate offer to be a promising material in energy storage devices with high energy.