Facile Synthesis of Nickel Cobalt Layered Double Hydroxide Nanosheets Intercalated with Sulfate Anion for High-Performance Supercapacitor

Abstract

Nickel-cobalt layered double hydroxide nanosheets intercalated with sulfate anion were fabricated via a facile hydrothermal method and investigated as high-performance electrode materials for supercapacitors. The morphology and electrochemical properties of the obtained samples could be controlled by changing molar ratios of the Ni and Co precursors. NiCo-LDHs with Ni/Co molar ratio of 0.35:0.65 exhibited high specific capacitance of 1551.1 F/g at the current density of 1 A/g and good cycling stability of 84.0% retention after 1000 charge/discharge cycles. On this basic, aqueous asymmetric supercapacitor (AAS) was successfully constructed by using the Ni_0.35Co_0.65-LDHs as the positive electrode and the activated carbon as the negative electrode. The as-built AAS was able to work in a working voltage window of 0~1.4 V and exhibited outstanding electrochemical performance. The Ni_0.35Co_0.65-LDHs//KOH activated cotton-derived carbon (ACDC) AAS showed the highest specific capacitance of 157.5 F/g, the satisfactory capacitance retention of 78.62% after 5000 cycles, the maximum energy density of 42.88 Wh/kg, and preferable combination of energy density of 30.63 Wh/kg with power density of 4.9 kW/kg at a current density of 7 A/g.