Honeycomb-Like Interconnected Network of Nickel Phosphide Heteronanoparticles with Superior Electrochemical Performance for Supercapacitors

Transition-metal-based heteronanoparticles are attracting extensive attention in electrode material design for supercapacitors owing to their large surface-to-volume ratios and inherent synergies of individual components; however, they still suffer from limited interior capacity and cycling stability due to simple geometric configurations, low electro-chemical activity of the surface, and poor structural integrity. Developing an elaborate architecture that endows a larger surface area, high conductivity, and mechanically robust structure is a pressing need to tackle the existing challenges of electrode materials. This work presents a supercapacitor electrode consisting of honeycomb-like biphasic Ni5P4-Ni2P (NixPy) nanosheets, which are interleaved by large quantities of nanoparticles. The optimized NixPy delivers an ultrahigh specific capacity of 1272 C g(-1) at a current density of 2 A g(-1), high rate capability, and stability. An asymmetric slipercapacitor employing as-synthesized NixPy as the positive electrode and activated carbon as the negative electrode exhibits significantly high power and energy densities (67.2 W h kg(-1) at 0.75 kW kg(-1); 20.4 W h kg(-1) at 15 kW kg(-1)). These results demonstrate that the novel nanostructured NixPy can be potentially applied in highperformance supercapacitors.