Tannic acid as a pioneering chelating agent for nickel–cobalt supercapacitor electrodes

Abstract

This study explores the innovative application of tannic acid (TA) in the synthesis of nickel-cobalt (Ni-Co) bimetallic compounds for supercapacitor electrodes. It examines the impact of hydrothermal treatment and calcination on the structure and performance of the materials. The results indicate that, due to the chelation of phenolic hydroxyl groups in TA with nickel and cobalt ions, hydrothermal conditions facilitate the formation of needle-like arrays of metal–organic coordination crystals, which can effectively increase the specific surface area of the electrode. The optimally synthesized electrode demonstrates an exceptional specific capacitance of 1337 F·g⁻¹ (668.5 C·g⁻¹) at a current density of 1 A·g⁻¹. Furthermore, when assembled into an asymmetric supercapacitor with activated carbon, it achieves a notably high energy density of 21.4 Wh·kg⁻¹ at a power density of 800 W·kg⁻¹. This superior performance is attributed to the higher specific surface area of the coordination crystals, which provides more active sites. These findings reveal that TA-modified Ni-Co bimetallic electrodes are promising for high-performance supercapacitors.