Two-dimensional porous zinc cobalt sulfide nanosheet arrays with superior electrochemical performance for supercapatteries

Abstract

Unique two-dimensional (2D) porous nanosheets with overwhelmingly rich channels and large specific surface area exhibit superior electrochemical capacitance performance, as compared to the conventional zero- and one-dimensional counterparts. As ternary transition metal sulfides (TMSs) are well recognized for their high electrochemical activity and capacity, and the replacement of oxygen with sulfur may result in high stability and flexible properties of the nanomaterials, as compared to transition metal oxides, herein we report the synthesis of 2D porous nanosheet arrays of ZnxCo1-xS (x = 0, 0.25, 0.5, 0.75, and 1) via a facile hydrothermal process. Due to the synergistic effect of the metal components and a unique 2D porous structure, the Zn0.5Co0.5S electrode was found to stand out as the best among the series, with a high specific capacity of 614 C g−1 at 1 A g−1 and excellent cycle retention rate of 90 % over 10, 000 cycles at 10 A g−1. Notably, a supercapattery based on a Zn0.5Co0.5S positive electrode and an activated carbon (AC) negative electrode (Zn0.5Co0.5S//AC) was found to display a 1.6 V voltage window, a 61 mA h g−1 specific capacity at 1 A g−1, a 49 Wh kg–1 energy density at 957 W kg–1 power density, and excellent cycling performance (88 % over 10, 000 cycles), suggesting tremendous potential of Zn0.5Co0.5S in the development of high-performance supercapattery devices.