Design of Three-Dimensional Nickel Foam/Carbon Fiber Composite Supported Nickel–Cobalt Hydroxides for High-Performance Supercapacitor Electrode Materials

Abstract

Hydroxides of nickel-cobalt have been widely employed as supercapacitor electrode materials. However, the shortcomings such as a low specific surface and an unstable structure made it difficult to display an excellent electrochemical performance. To address the said problems, carbon fibers were grown in situ on foam nickel by CVD method to prepare a three-dimensional foam nickel/carbon fiber composite collector, and then nickel-cobalt hydroxides were obtained on the composite current collector by a hydrothermal method with the aim of a superior supercapacitor electrode material (CF/Ni–Co). Effects of anions of metal salts (such as acetate, nitrate, sulfate and chloride) on the morphology, structure and electrochemical performance of the obtained electrodes were investigated. The results suggested that the sample CF/Ni–Co(SO₄) synthesized with nickel sulfate and cobalt sulfate possessed large specific surface area. It also displayed outstanding capacitive performance with a superb specific capacitance of 3675.6 F/g at 1 A/g, a high capacitance retention rate of 70.6% as the current density increased to 15 A/g, and a good cycling stability of 66.4% after 2000 cycles of charge-discharge at 15 A/g, demonstrating CF/Ni–Co(SO₄) with the three-dimensional nickel foam/carbon fiber composite as current collector had great potential for high-performance supercapacitor electrode materials.