Carbon layer coated nickel phosphide nanoparticles embedded in three-dimensional graphene network for high-performance supercapacitor

Transition metal phosphides (TMPs) are widely used as an electrode material because of their adjustable electronic structure, variable composition, and excellent electrical conductivity, which possess a broad application prospect in supercapacitors (SCs). The participation of carbon material is capable of enhancing the conductivity and electrochemical property of TMPs. Herein, carbon layer coated Ni2P nanoparticles embedded in a threedimensional graphene network (Ni2P@C@rGO) are elaborately designed by the chemical-blowing method and subsequently low-temperature phosphorylation. The optimal Ni2P@C@rGO exhibits excellent capacitance of 1338.8 F/g at 1 A/g with a good rate capability of 66% even up to 30 A/g. For further exploring the practical application value, asymmetric SCs (ASCs) are successfully constructed based on Ni2P@C@rGO and N-PCS (nitrogen-doped porous carbon sheet) fabricated using a one-step chemical-blowing method. As a result, the ASC shows an excellent energy density of 33.4 Wh/kg at a power density of 792.1 W/kg, and remarkable cycle stability (85.2% capacitance retention after 10,000 cycles at 10 A/g). Thus, the Ni2P@C@rGO exhibits very attractive candidate as electrode material in high-performance energy-storage devices.