A high-temperature phosphorization for synthesis of core-shell Ni-NixPy@C nanocomposite-immobilized sponge-like P-doped porous carbon with excellent supercapacitance performance

To effectively enhance the overall electrochemical performance of supercapacitors , a high-temperature phosphorization strategy was developed to fabricate core-shell Ni-Ni x P y @C nanocomposite-immobilized sponge-like P-doped porous carbon (Ni-Ni x P y @C/P-HPC). The Ni-Ni x P y @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-Ni x P y nanoparticles , forming core-shell Ni-Ni x P y @C nanocomposites, doping P element into carbon skeleton and immobilizing core-shell Ni-Ni x P y @C nanocomposites onto porous carbon, were achieved simultaneously. The Ni-Ni x P y @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-Ni x P y @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.