Preparation And Supercapacitive Properties Of Nickel-cobalt Bimetallic Sulfide Based Nanocomposites

In order to improve the supercapacitive performance of metal sulfide electrode materials,sulfide nanoparticles with different ratios nickel-cobalt were prepared by one-step hydrothermal method,and prepared sulphide were further hybrid with g-C₃N₄ and CNTs.The effects of nickel-cobalt atomic ratio and carbon nano-material content on the morphology,structure and supercapacitor properties of metal sulfides were investigated systematically.Based on these results,high-performance asymmetric supercapacitors were assembled.The main research contents and conclusions are as follows:1.NiCo₂S₄,Ni_1.5Co_1.5S₄ and Ni₂CoS₄ nanoparticles were prepared by one-step hydrothermal method.The results show that the samples are all coral reef-like morphology assembled by irregular small particles with good crystallinity.The Ni_1.5Co_1.5S₄ sample has a particle size of about 10-60 nm and good dispersibility.The three-electrode system test shows that Ni_1.5Co_1.5S₄ exhibits the best pseudocapacitor performance.The Ni_1.5Co_1.5S₄ electrode shows a high specific capacity of 1191 Fg^-1 at a current density of 1 Ag^-1.The specific capacity reaches the 852 Fg^-1 at a current density of 20 Ag^-1.2.The nickel-cobalt sulfide/g-C₃N₄ nanocomposites were prepared using one-step hydrothermal metod by introduing g-C₃N₄ nanosheets.The results show that Ni_1.5Co_1.5S₄ nanoparticles are grown in situ on overlapping g-C₃N₄ nanosheets,forming the porous g-C₃N₄ framework structure.When the content of g-C₃N₄ is 10wt.%,the composite exhibits the best pseudocapacitive properties.The specific capacity reaches 1827 Fg^-1 at the current density of 1 Ag^-1.As the current density is20 Ag^-1,the specific capacity reaches the 1348 Fg^-1,with capacitance retention of73.78%.The assembled Ni_1.5Co_1.5S₄/g-C₃N₄//AC asymmetric supercapacitor delivers a high energy density of 49 Wh kg-1 at a power density of 799 W kg^-1.The energy density is still up to 27 Wh kg^-1 at a power density of 15.94 kW kg^-1.The capacitance retention is 95%after 8000 cycles at the current density of 10 Ag^-1.3.The nickel-cobalt sulfide/CNTs nanocomposites were prepared using one-step hydrothermal metod by introduing multi-wall CNTs.The results show that Ni_1.5Co_1.5S₄ nanoparticles coated on the surface of the CNTs,and the CNTs play a supporting role in the composite materials.When the content of CNTs is 10 wt.%,the composite exhibits the best pseudocapacitive properties.The specific capacity reaches1894 Fg^-1 at the current density of 1 Ag^-1.As the current density is 20 Ag^-1,the specific capacity reaches the 1431 Fg^-1,with capacitance retention of 75.55%.The assembled Ni_1.5Co_1.5S₄/CNTs//AC asymmetric supercapacitor provides a high energy density of 61.15 Wh kg-1 at a power density of 800 W kg^-1.The energy density is still up to 34.84 Wh kg^-1 at a power density of 16.8 kW kg^-1.The capacitance retention is95%after 8000 cycles at the current density of 10 Ag^-1.