Effective preparation of Ni1.4Co0.6P@C micro-spheres with prolonged cycling lives for high performance hybrid supercapacitors

In order to effectively enhance the performances of supercapacitors (SCs), novel electrode materials with high energy density and long cycling lives are urgently needed. Herein, we provide an universal strategy to improve the cycling stablity of transition metal phosphides as supercapacitor electrodes. Ni1.4Co0.6P@C hierarchical core@shell microspheres with abundant electrochemical active sites for large energy storage and coated porous carbon shells for drastically improved conductivity and cycling stability are purposely prepared and obtained. Benefiting from its excellent structural and compositional advantages, the as-derived Ni1.4Co0.6P@C microspheres possess attractive electrochemical properties such as remarkably high specific capacitance (1571.3 F g−1 at 1 A g−1), good rate capability (80.2%, from 1 A g−1 to 25 A g−1), and outstanding cycling stability (retained 82.8% after 5000 cycles). The fabricated all-solid state asymmetric supercapacitor using Ni1.4Co0.6P@C spheres and hollow carbon nanospheres (HCNs) as electrodes delivers the energy density of 40.8 Wh∙kg−1 at a power density of 80.8 W kg−1 and excellent cycling stability (retained 89.3% after 10000 cycles), illustrating its promising application potentials.