Preparation of Ni-Co selenide as long-cycling electrode material of supercapacitor

Transition metal selenide as supercapacitor electrode materials has been extensively studied and exhibits promising electrochemical performance. However, the poor cycling durability affects its practical application. Here, a design for the fabrication of nickel-cobalt selenide is presented. ZIF-67 was firstly synthesized and then the Ni element was introduced to fabricated precursor, which was then converted into selenides by hydrothermal reaction, in the presence of selenium powder and sodium borohydride. Results show that molar ratio of Co/Ni influences the crystalline phase, particles dispersion state and properties of the obtained selenides. The selenide obtained at optimized molar ratio of Co/Ni (1/1) shows high specific capacitance (1234.2 F g(-1) at current density of 1 A g(-1)) and excellent cycling durability (76.0 % of the specific capacitance after 10000 cycles). The outstanding performance may be due to the proper composition and microstructure brought out by the proper Co and Ni molar ratio.