Pseudo-capacitance of ultrafine nickel hydroxide prepared by sol-gel method

Abstract

A new sol-gel process for the preparation of ultrafine nickel hydroxide electrode materials was developed. The particle size and configuration of the nickel hydroxide product can be controlled with polyethylene glycol. The hydroxide praticles have a diameter range of 100-200 nm and take on an unique chain-bead like configuration. The composite electrodes consisting of carbon nanotubes and Ni(OH)2 were developed by mixing the hydroxide and carbon nanotubes together in varous ratios. A maximum capacitance of 320 F·g-1 was obtained for the composite electrode containing 20% carbon nanotubes compared with that of activated carbon (184 F·g -1). The performance of a newly designed combined electrochemical capacitor was evaluated. The capacitor was prepared by using nickel hydroxide/carbon nanotubes composite as a positive electrode and activated carbon as a negative electrode. Values for the specific energy and maximum specific power of 20.11 W·h·kg-1 and 8.6 W· g-1, respectively, were demonstrated for a cell voltage between 0 and 1.6 V. By using the modified anode of a Ni(OH)2/carbon nanotubes composite electrode, the combined supercapacitor exhibited high energy density and stable power characteristics.