To effectively enhance the overall electrochemical performance of supercapacitors, a high-temperature phosphorization strategy was developed to fabricate core-shell Ni-NixPy@C nanocomposite-immobilized sponge-like P-doped porous carbon (Ni-NixPy@C/P-HPC). The Ni-Ni-NixPy@C/P-HPC was successfully constructed by a cross-linking process and subsequent high-temperature calcination. During the pyrolysis process in N-2 multiple steps, including phosphating metal ions to Ni-NixPy nanoparticles, forming core-shell Ni-NixPy@C nanocomposites, doping P element into carbon skeleton and immobilizing core-shell Ni-NixPy@C nanocomposites onto porous carbon, were achieved simultaneously. The Ni-NixPy@C/P-HPC was studied using various characterization techniques. The results revealed that the obtained material integrated the advantages of interconnected P-doped framework (fast ion transport), nickel and nickel phosphide species (high theoretical specific capacitance), and graphene-like shell (excellent electrical conductivity and effective protection for activate sites). Therefore, the as-prepared hybrid delivered the outstanding electrochemical performance with ultrahigh specific capacity of up to 1275 F g(-1) at 1 A g(-1) and an excellent cycling stability with 92.5% capacity retention after 5000 cycles. Besides, the asymmetric supercapacitor using Ni-NixPy@C/P-HPC-900 and activated carbon as the anode and cathode materials exhibited a high energy density of 49.4 W h kg(-1) at 250 W kg(-1), and remained as high as 30.6 W h kg(-1) even at 5000 W kg(-1). Our research will open up a new way to synthesize transition metal phosphide@carbon composites with excellent electrochemical properties. (C) 2019 Elsevier Ltd. All rights reserved.