Battery-type and binder-free MgCo2O4-NWs@NF electrode materials for the assembly of advanced hybrid supercapacitors

In this study, the hetero-structure of MgCo₂O₄ nanowires (MCO-NWs) and microcubes (MCO-MCs) on the skeleton of nickel foam (NF) was realized through a simple hydrothermal method and subsequent annealing treatment, and then served as a binder-free cathode for assembly of high-performance hybrid supercapacitor (HSC). Such synthetic methodology avoided the traditional usage of conductive and binder reagents for the electrode fabrication. The electrochemical tests indicated its battery-type characteristics, and the MCO-NWs@NF exhibited a huge specific capacity (C_s) of 389.0 C g^?1 as well as 86.2% capacity retention when the current density boosted from 1 to 10 A g^?1. The assembled HSC with activated carbon (AC) as anode further demonstrated the advantages of this electrode material. After 5000 cycles at 6 A g^?1, the MCO-NWs@NF//AC HSC showed good long-term cycling stability without any decay in capacitance, and could deliver an energy density (E_d) of 37.9 W h kg^?1 at the power density (P_d) of 958.1 W kg^?1, higher than the 30.4 W h kg^?1 of MCs-based HSC. These impressive results regarding electrochemical performance suggest that MCO-NWs@NF may be a promising candidate to serve as a battery-type material in electrochemical energy storage applications such as HSCs, batteries, and so on.