Hydrothermal Synthesis of Zn_x Ni_1-x S Nanosheets for Hybrid Supercapacitor Applications

Nickel-foam-supported Zn_x Ni_1-x S nanosheets are synthesized by a two-step hydrothermal method. The Zn_x Ni_1-x S nanosheets can be considered as the product of the partial substitution of Zn²⁺ ions by Ni²⁺ ions in the ZnS lattice. The resulting Zn_x Ni_1-x S/Ni foam can be directly used as an electrode for supercapacitors. It can reach a specific capacitance of 1412 F g^-1 at a current density of 1 Ag^-1 with 68.0 % capacitance retention at 16 Ag^-1 . Control experiments show that the electrochemical performances of Zn_x Ni_1-x S nanosheets are much better than those of ZnS and NiS prepared under the same conditions. Furthermore, a hybrid supercapacitor device was assembled by using the Zn_x Ni_1-x S nanosheets as the positive electrode and porous carbon as the negative electrode; the device exhibited high power and energy densities. This study demonstrates that the construction of bimetal sulfides is a strategy to develop high-performance supercapacitor electrode materials.