2D Nanoflakes of metal-polyphenolic coordination assembly for high-performance supercapacitor

Abstract

A novel metal-polyphenol assembly is successfully prepared through the coordination of Ni2+ and a natural polyphenol ellagic acid (EA), leading to a stable micro-sized particle composed of two-dimensional (2D) nanoflakes. As electrode materials for supercapacitors, the Ni-EA coordination materials display a high capacitance of 1050Fg−1 at the current density of 0.5Ag−1. Besides, an asymmetric supercapacitor (ASC) is assembled by using the Ni-EA nanoflakes as the positive electrode and activated carbon (AC) as the negative electrode. The ASC presents a high energy density of 31.22Whkg−1 at a power density of 800Wkg−1 and superior cycling stability with 91.8% specific capacitance retention over 4000cycles at a high current density of 10Ag−1. These results demonstrate the Ni-EA nanoflakes are promising electrode materials for high-performance supercapacitor.