Synthesis of CuCo2S4 nanosheet arrays on Ni foam as binder-free electrode for asymmetric supercapacitor

Recently more and more concerns have been paid on ternary metal sulfides for use in supercapacitors because of their better electrochemical performances compared with binary counterparts. In this work, CuCo2S4 nanosheet arrays on Ni foam were prepared by a sequential ion-exchange strategy under hydrothermal conditions, where Co3O4 was converted into Co4S3 by an anion-exchange reaction between Co3O4 and S2- ions, subsequently the Co4S3 was transformed into CuCo2S4 through a cation-exchange reaction with Cu2+ ions. The as-prepared CuCo2S4 was characterized by powder X-ray diffraction, high-resolution X-ray photoelectron spectroscopy, field emission scanning electron microscopy and transmission electron microscopy. The CuCo2S4 arrays were composed of interconnected thin nanosheets with thickness of about 10 nm. The CuCo2S4 nanosheet arrays on Ni foam were directly employed as a binder-free electrode showing a high specific capacitance of 3132.7 F g(-1) at a current density of 1 A g(-1). Besides, an asymmetric supercapacitor based on this synthesized CuCo2S4 electrode as positive electrode and active carbon as negative electrode can deliver a high energy density of 46.1 Wh kg(-1) at a power density of 991.6 W kg(-1), and exhibits good rate capability and cycling stability. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.