Partial Ion-Exchange of Nickel-Sulfide-Derived Electrodes for High Performance Supercapacitors

Abstract

A novel method to adjust the composition of a material while maintaining its morphology was described in this study. Nickel sulfide, the material investigated in this work, was found to be useful as a high surface area electrode material for supercapacitor applications. First, a nest-like Ni3S2@NiS composite electrode with 1D nanorod as structural unit was synthesized by simultaneously using Ni foam as template and Ni as a source through a one-step in situ growth method. Co and Se ions, which respectively acted as beneficial cation and anion, were successfully introduced into the nest-like Ni3S2@NiS material, resulting in the formation of Ni3S2@Co9S8 and NiS@NiSe2 composite electrodes with structures similar to those of the parent materials. The material structure was virtually retained and single-crystal-to-single-crystal transformation was achieved in the process. Introducing the cation and anion into the same type of material while maintaining topology could be important for the field of material synthesis and preparation of supercapacitor electrodes. Moreover, the electrochemical properties of these three materials were studied by cyclic voltammetry measurements and galvanostatic charge–discharge tests. The results indicated that the rate performance was improved significantly by ion exchange. In particular, the derived electrode with Se still showed superior oxidation and reduction ability at high scan rate of 10000 mV s–1. In addition, the second charge–discharge specific capacity also increased from 516 F g–1 to 925 F g–1 and 1412 F g–1 at the current density of 0.5 A g–1 and by Co and Se exchange, respectively. This work contributes to the knowledge on electrode materials for supercapacitors and can provide good reference for the fabrication of desired materials.