Core-shell structured Ni3S2@Co(OH)2 nano-wires grown on Ni foam as binder-free electrode for asymmetric supercapacitors

Core-shell structured Ni3S2@Co(OH)2 nano-wires directly grown on Ni foam as a binder-free electrode for asymmetric supercapacitors are synthesized though a facile two-step process. This unique core–shell architecture consisting of ultrathin Co(OH)2 nano-sheets and Ni3S2 nano-wires exhibits significantly enhanced electrochemical capacitive performance. The Ni3S2@Co(OH)2 electrode demonstrates high specific capacitance of 2139.4 F g−1 at the current density of 2 mA cm−2, and retains capacitance of 1139.4 F g−1 at a much higher current density of 40 mA cm−2. An asymmetric supercapacitor using Ni3S2@Co(OH)2 as cathode and active carbon as anode is successfully assembled in a coin cell. The as-prepared cell delivers high-power density as high as 18.27 kW kg−1 at the energy density of 74.79 Wh kg−1 with good cycling stability, which shows its feasibility for many practical applications for energy storage. These results indicate that the newly developed core-shell architecture is an efficient way towards improve the electrochemical performance in various promising energy storage applications.