Porous NiCoP nanowalls as promising electrode with high-area and mass capacitance for supercapacitors

The design of the electrode with high-area and mass capacitance is important for the practical application of supercapacitors. Here, we fabricated the porous NiCoP nanowalls supported by Ni foam (NiCo-P/NF) for supercapacitors with win-win high-area and mass capacitance. The NiCoOH nanowall precursor was prepared by controlling the deposition rate of Ni2+ and Co2+ on NF through a sodium acetate-assisted (floride-free) process. After the phosphorization, the NiCo-P nanowalls formed with high loading about 8.6 mg cm-2 on NF. The electrode combined several advantages favorable for energy storage: the plentiful pores beneficial for ion transport, the nanowalls for easy accommodation of electrolyte, good conductivity of NiCo-P for easy transport of electrons. As expected, the NiCo-P/NF exhibited a high specific mass capacitance (1,861 F g-1 at 1 A g-1, 1,070 F g-1 at 10 A g-1), and high area capacitance (17.31 F cm-2 at 5 mA cm-2 and 10 F cm-2 at 100 mA cm-2). The asymmetric supercapacitor (ASC) composed of NiCo-P/NF positive electrode coupled with commercial active carbon negative electrode exhibited a high energy density of 44.9 W h kg-1 at a power density of 750 W kg-1. The ASC can easily drive fans, electronic watch and LED lamps, implying their potential for the practical application.