3D nickel-cobalt phosphide heterostructure for high-performance solid-state hybrid supercapacitors

Transition-metal phosphides are emerging candidates for supercapacitors owing to their high conductivity and electrochemical activity. It still remains a great challenge to develop phosphide-based supercapacitors with advanced phosphide architectures and optimized device components, which are crucial for realizing their high-energy storage. Herein, hierarchical Ni–Co–P heterostructure assembled by porous nanoplates is achieved. It displays the metalloid property, multi-component synergy, high reaction activity, and rapid electron transfer/ion diffusion behavior. Benefitted from these merits, Ni–Co–P offers respectable gravimetric capacity and high-rate capability (653 and 470 C g−1 at 1 and 30 A g−1) over Ni–P (520 and 39 C g−1) and Co–P (169 and 122.4 C g−1). Moreover, the areal capacity of 5.8 C cm−2 at 1 A g−1 is delivered under high mass loading of 15 mg cm−2. When integrating Ni–Co–P as positive electrode material and active carbon as negative electrode material, the developed hybrid supercapacitor with PVA/KOH gel electrolyte presents prominent energy/power density of 30.2 Wh kg−1/12620 W kg−1 with superior cycling stability of 10,000 times. It can also light the LED indicator, and work well in a temperature range of -10–60 °C. This research enriches the energy-related material system and boost the development of existing energy devices.