Flower-like nickel hydroxide@tea leaf-derived biochar composite for high-performance supercapacitor application

Abstract

Renewable and sustainable high-performance energy storage devices are desirable to fulfill the demands of next-generation power sources. In this study, we report a flower-like nickel hydroxide/spent tea leaf-derived biochar (NiNF@TBC) composite for high-performance supercapacitor application. The tea leaf-derived biochar (TBC) with a specific surface area of 1340 m2 g−1 is used as the Ni(OH)2 support to fabricate NiNF@TBC composites. The highly porous and hierarchical structure of the as-synthesized NiNF@TBC composite facilitates the electrolyte ion and electron diffusion and transport more readily. As a result, the decrease in diffusion path and the increase in conductivity of NiNF@TBC for energy storage applications. The NiNF@TBC electrode shows excellent electrochemical properties with a specific capacitance of 945 F g−1 at 1 A g−1 in a three-electrode cell and high stability of 95% after 10,000 cycles. Moreover, the symmetric supercapacitor fabricated with NiNF@TBC delivers a specific capacitance of 163 F g−1 in 1 M Na2SO4 solution. The Ragone plot of the symmetric device exhibits energy density in the range of 19 – 58 Wh kg−1 with power density in the scale of 826 – 6321 W kg−1. An excellent long-term cyclic stability of 94% is obtained after 10,000 charge–discharge cycles. Such an excellent performance has demonstrated the feasibility of utilizing agricultural wastes as green carbon sources, which can combine with various metal hydroxides to produce hybrid nanomaterials as a highly potential electrode material for green sustainable supercapacitor applications.