Rapid In-situ Growth of β-Ni(OH)2 Nanosheet Arrays on Nickel Foams as Integrated Electrodes for Supercapacitors Exhibiting High Energy Density

Ni(OH)2 has been widely investigated as a prospective electrode material because of its high theoretical capacitance and relatively low cost. However its synthesis usually needs complex and lengthy process, and binder is generally used in fabricating the Ni(OH)2 based electrodes. In this work, self-supporting binder-free β-Ni(OH)2@nickel foam (NF) integrated electrode was prepared by in-situ growth of β-Ni(OH)2 on NF using a rapid and facile approach. This approach consists of two processing steps: (1) a pre-treatment of NF with acid and (2) a quick in-situ electrochemical synthesis of β-Ni(OH)2 on NF in KOH electrolyte within half a minute under an applied voltage. The β-Ni(OH)2@NF integrated electrode possesses a three-dimensional network structure of nanosheet arrays, and exhibits excellent electrochemical performance. Its areal capacity is 3.68 mAh cm-2 at the current density of 2 mA cm-2, and the capacity can reach 115.8% of the initial value even after 2000 cycles under a current density of 15 mA cm-2. Moreover, the as-assembled β-Ni(OH)2@NF//activated carbon (AC) asymmetric supercapacitor (ASC) exhibits a high energy density of 74.2 Wh kg−1 with a power density of 776.9 W kg−1 as well as an excellent cycling stability (89.9% retaining after 10000 cycles). This work provides an efficient, facile and economic method for fabricating Ni(OH)2 based integrated electrode for high-performance supercapacitors.