Solvothermal synthesis of weakly crystalline cobalt–nickel sulfide to obtain high pseudocapacitance

In this paper, a dual solvent system of glycerol and ethylene glycerol was used to prepare nickel cobalt sulfide with different crystallinities. It was found that the crystallinity and morphology of the product had an important effect on its electrochemical performance. Therefore, the synthesis time was chosen between 1 and 18 h to control the crystallinity. The best sample (GENCS-3) was prepared within 3 hour and had flower-like structures. Its electrochemical tests showed that it had good ion transmission efficiency and excellent specific capacitance (1816 F/g at 1 A/g, 1620 F/g at 10 A/g). Especially, its retention rate could arrive at 89.4% after 1000 cycles under a current density of 5 A/g. The weak crystalline nickel–cobalt sulfide is easy to form porous structure, which can significantly increase capacitance, also maintaining good rate performance.