Spinel NiCo2O4 for use as a high-performance supercapacitor electrode material: Understanding of its electrochemical properties

Abstract

In this work, spinel NiCo<inf>2</inf>O<inf>4</inf> is prepared by a facile sol-gel method with the effect of three different chelating agents including citric acid (CA), oxalic acid (OA) and ethylenediamine tetraacetic acid (EDTA) explored upon the fabrication methodology and resulting electrochemical and supercapacitor properties. The electrochemical measurements reveal that NiCo<inf>2</inf>O<inf>4</inf> prepared using OA exhibits ultrahigh specific capacitance of 1254 F g^-1 at 2 A g^-1 due to the resultant high specific surface area, while NiCo<inf>2</inf>O<inf>4</inf> prepared by EDTA exhibits the best rate capability and cycling stability owing to the subsequent large pore size. The obvious differences can be primarily ascribed to the use of the differing chelating agents which are shown, for the first time, to greatly affect the particle size, pore structure and specific surface area of the fabricated NiCo<inf>2</inf>O<inf>4</inf>. Such work is of fundamental importance and demonstrates that the tailoring of these different properties can be readily obtained through the use of differing chelating and is responsible for the observed differing electrochemical properties. Additionally, first-principles calculations were employed to investigate the electronic structure of NiCo<inf>2</inf>O<inf>4</inf>, which can help to further understand its excellent electrochemical behaviors. These results above provide a facile, cost-effective and high-performance strategy for supercapacitor electrode applications. © 2014 Elsevier B.V. All rights reserved.