Uniform P doped Co-Ni-S nanostructures for asymmetric supercapacitors with ultra-high energy densities.

Uniform P doped Co-Ni-S nanosheet arrays were directly grown on Ni foams by an efficient and cost-effective process. The binder-free electrode of P doped Co-Ni-S nanosheet arrays possesses an ultra-high specific capacitance of ∼3677 F g-1 at 1 A g-1 with an excellent rate capability (∼63% capacitance retention at 20 A g-1) and considerable cycling performance (∼84% capacitance retention after 10 000 cycles). Correspondingly, the asymmetric supercapacitors assembled with P doped Co-Ni-S as the positive electrode and AC as the negative electrode display an ultra-high energy density of ∼68.7 W h kg-1 at a power density of ∼0.8 kW kg-1. In view of these features, this work provides a simple and scalable strategy for designing electrodes and devices with superior electrochemical performance in next generation energy storage applications.