Cauliflower-like Ni/NiCoP@Boron-doped diamond composite electrodes for high-performance symmetric supercapacitors

Due to the lack of electrocatalytic active sites, the supercapacitors (SCs) even based on the most stable sp3 carbon material (Boron-doped diamond) suffer from poor capacitance and low energy density. Herein, a cauliflower-like biphasic Ni/NiCoP layer has been successfully deposited on the BDD film and further applied as binder-/current collector-free SC electrodes. In a redox-active aqueous electrolyte (0.05 M Fe(CN)63−/4− + 1.0 M KOH), the Ni/NiCoP@BDD electrode with exceptional cyclic stability (∼89.0 % after 10,000 cycles) delivers a specific capacitance of 256.1 mF cm−2 at a current density of 30 mA cm−2, about 2 times higher than that in inert electrolyte. Furthermore, such a symmetric PC device provides a desired energy density of 70.0 Wh kg−1 at a high power density of 3601 W kg−1. [Display omitted]