Core-shell structured Ni₃S₂ nanorods grown on interconnected Ni-graphene foam for symmetric supercapacitors

We report the synthesis of mesoporous Ni₃S₂ nanorod arrays on three-dimensional Ni-graphene foams by a facile hydrothermal method for ultrahigh performance supercapacitors. The graphene foam facilitates unique morphological evolution during the hydrothermal process, from a mesoporous, monolithic structure to nanorod arrays of Ni₃S₂ with a hollow core-solid shell structure and to entirely solid nanorod arrays of Ni₃S₂. The Ni₃S₂ composite electrode delivers a remarkable specific capacitance of 1900 F g⁻¹ at a current density of 1 A g⁻¹, as well as promising cyclic stability with a high capacitance of 940 F g⁻¹ after 2000 cycles at 10 A g⁻¹ and 96% retention of its initial capacitance after the 2001^st cycle at 5 A g⁻¹. The symmetric supercapacitor prepared using the Ni₃S₂ electrodes under an optimum condition operates in a wide potential window of 0–1.6 V and offers a specific capacitance of 190.5 F g^-1 at 4.5 mA cm⁻² along with a maximum energy density of 67.7 W h kg^-1. The promising electrochemical performance along with the facile synthesis strategy offers a new insight into developing high performance supercapacitors for emerging energy storage applications.