One-step solid-state synthesis of NixPy @C nanocomposites for high-performance hybrid supercapacitor

Transition metal phosphides and their composites are very attractive ascribing to their prominent performance in electrochemical energy storage devices, which are generally prepared by cumbersome and time-consuming liquid-phase synthesis methods. In this work, a convenient and efficient one-step solid-phase synthesis method (SPS) is successfully developed for the preparation of NixPy @C nanocomposites under the ambient atmosphere. By controlling the synthesizing temperature, carbon-coated Ni2P, Ni5P4, and NiP2 nanocomposites can be facilely synthesized. The solid-phase synthesized NixPy @C nanocomposites exhibit high charge storage capability and good cycle stability. A high specific capacity of over 197.2 mAh g−1 (709.9 C g−1) is achieved at a current density of 1 A g−1 for the optimal nanocomposite NiP2 @C, and more than 84.3% of initial specific capacitance is kept after 1000 cycles. The assembled hybrid supercapacitor device based on the nanocomposite NiP2 @C and an interconnected hierarchical porous carbon (NiP2 @C//IHPC) delivers specific energy of up to 50.38 Wh kg−1 at the specific power of 0.89 kW kg−1, which value still reaches 29.1 Wh kg−1 at a high specific power of 9.44 kW kg−1. More than 83.8% of initial specific capacity is retained after 20,000 cycles. Compared with the other nickel-based phosphides and their composites prepared by other methods, the prepared NixPy @C nanocomposites by the developed one-step SPS method demonstrate very competitive performance with the distinguished merits of convenient, efficient, target-oriented, cost-efficiency, and eco-friendly. The successfully developed solid-phase synthesis method is proved to be a reliable strategy for facile preparation of TMPs with high performance.