Asymmetric supercapacitors(ASCs) have the merits of rapid charge and discharge,high power density,and long?term cyclic stability.The properties of electrode materials determine the performance of ASCs.Cation substitution is an effective method to tune the structure and properties of electrode materials and optimize energy storage performance accordingly.This paper prepared MCo2S4(M=Co,Ni,or Cu) nanosheet arrays on the surface of a nickel foam substrate.For this purpose,it controlled the cationic components of the spinel sulfide and employed a hydrothermal method.Due to the differences in the radius and electronegativity of metal irons,the lattice structure of Co3S4 underwent strain when Ni2+ or Cu2+ ions were introduced into Co3S4 to obtain NiCo2S4 or CuCo2S4.The result was reinforced reactivity of the metal sites.The charge transfer and ion diffusion resistances of NiCo2S4 are respectively 48.6% and 28.7% lower than those of Co3S4,indicating favorable electrochemical properties achieved.The specific capacity of NiCo2S4 is 1 128.8 F/g under a current density of 1 A/g.The capacity retention is 59.8% under a current density of 10 A/g.The retention of the initial specific capacity is 60.2% after 8 000 cycles.