NiCo2O4/NiCoP nanoflake-nanowire arrays: a homogeneous hetero-structure for high performance asymmetric hybrid supercapacitors

Abstract

Transition metal phosphides (TMPs) represent an important class of compounds with metalloid characteristics and good electrical conductivity, which are of great benefit to enhance electrochemical performances. Thus it is important to clarify the correlation between the electrochemical properties and the phosphating degree of the precursor. Herein, we report a superior electrode for battery-like capacitors based on NiCo₂O₄/NiCoP hetero-structure nanoflake-nanowire arrays grown on nickel foams using a one-pot facile hydrothermal approach and a controllable phosphorization treatment method. The Ni–Co precursor nanoflake-nanowire array based electrode treated with 500 mg NaH₂PO₂ shows significantly improved electrochemical performances with an ultrahigh specific capacitance of 2288.8 F g⁻¹ and 1644 F g⁻¹ at a current density of 1 A g⁻¹ and 20 A g⁻¹, respectively. The electrode also shows superior cycling stability. In addition, the NiCo₂O₄/NiCoP//AC device exhibits a relatively high energy density of 35.5 W h kg⁻¹ at 750.4 W kg⁻¹. The results suggest that this NiCo₂O₄/NiCoP nanoflake-nanowire array is a promising electrode material for high performance hybrid supercapacitor applications.