Controllable and fast growth of ultrathin α-Ni(OH)2 nanosheets on polydopamine based N-doped carbon spheres for supercapacitors application

Abstract

Rational design of structures plays a key role in achieving high capacitive performances for electrode materials of supercapacitors. In this study, polydopamine based N-doped carbon spheres (NCSs)@Ni(OH)2 nanocomposites with integrated core-shell structure are developed, in which ultrathin nanosheets of α-Ni(OH)2 are vertically and tightly grafted on NCSs by a fast and scalable chemical bath deposition method. The conductive skeleton of NCSs not only facilitates fast electron transfer, but also enhances the structure stability of α-Ni(OH)2. The effects of synthetic conditions such as NCSs content, deposition time of Ni(OH)2 and oxidant amount on the morphology, structure and capacitive performance of NCSs@Ni(OH)2 nanocomposites are thoroughly investigated. The optimized nanocomposite exhibits excellent electrochemical performances with ultrahigh specific capacitance of 840 C g−1 at 2 A g−1 and 640 C g−1 even at ultrahigh current density of 20 A g−1. Based on NCSs@Ni(OH)2, the hybrid supercapacitor shows maximum energy density of 33.5 Wh kg−1 at the power density of 0.4 kW kg−1 and the energy density still remains 20.4 W h kg−1 when the power density increases to 4 kW kg−1.