One-step colloid fabrication of nickel phosphides nanoplate/nickel foam hybrid electrode for high-performance asymmetric supercapacitors

Supercapacitors, which can supply superior energy density compared to conventional dielectric capacitors and higher power density than batteries, have attracted considerable attention as a promising energy storage device. However, cycle performance and specific energy density are still key factors limiting its practical applications. This work reports a facile synthesis of high-performance asymmetric supercapacitors with hybrid nickel phosphides/ nickel foam as positive electrode and biomass-based sulfur-doped hierarchical porous activated carbon as negative electrodes. It demonstrates a novel one-step colloid synthesis of nickel phosphides directly on commercial nickel foam as only nickel source. The obtained electrode exhibits satisfactory specific capacity of 1032 C g(-1) (2293 F g(-1)) at 1 A g(-1) and cyclic stability over 10,000 cycles. Most importantly, the fabricated asymmetric supercapacitor devices show excellent cyclic stability with 85.7% capacitance retention after 10,000 cycles and deliver a maximum energy density of 42.2 Wh kg(-1) at 741.1Wkg(-1) power density. To the best of our knowledge, the assembled device in this report has absolute advantages in fields requiring simultaneous high energy density and long-term operation at high current density. These promising results demonstrate the possibility of a facile synthesis of efficient asymmetric supercapacitors with high electrochemical response and cycling stability.