Fingerprint-like NiCoP electrode material with rapid charging/discharging performance under large current density

Abstract

Supercapacitance electrode materials with rapid charging/discharging performance are considerably useful in practical applications for time saving. However, the supercapacitance performance of the electrode materials is sharply degraded with the increase in current density. To achieve fast energy storage for portable devices, bimetallic nickel cobalt phosphides (NiCoPs), composed of special fingerprint-like nanosheets (NSs), are developed as electrode materials, which exhibit a high specific supercapacitance under large charging/discharging current density. The NiCoP NSs are assembled using entangled nanowires with a wide pore size distribution through hydrothermal and phosphorization reactions. The influence of phosphorization temperature on the morphologies, chemical compositions, and supercapacitance performance of NiCoP compounds is investigated. Electrochemical tests show that the fingerprint-like NiCoP NSs deliver a high specific capacitance of 2360, 1900, and 900 F g−1 at 1, 20, and 50 A g−1, respectively, indicating outstanding capacity retentions of 81% (1–20 A g−1) and 38% (1–50 A g−1) at large charging/discharging current density. The assembled asymmetric supercapacitor of NiCoP//activate carbon presents an energy density of 156 Wh kg−1 at 1331 W kg−1 and maintains 67.5 Wh kg−1 at 27000 W kg−1 in aqueous KOH electrolyte. The bimetallic NiCoPs with a tunable fingerprint-like structure can enhance conductivity, provide nanoporous channels, and facilitate fast electrochemical reactions, which are remarkably beneficial for rapid energy storage and conversion applications.