Preparation Of Nickel-cobalt Sulfide By Room Temperature Vulcanization Method And Its Application In Supercapacitors

With the continuous advancement of human society science and technology,it is extremely urgent to develop an environment-friendly and energy-saving energy storage device.Supercapacitors are standard low carbon economy products and are ideal energy storage devices.In recent years,transition metal oxides,hydroxides,and sulfides have been widely used as research objects for supercapacitor electrode materials due to their high theoretical specific capacity.The paper briefly describes the characteristics,composition,energy storage mechanism and application of supercapacitors,and reviews the current development status and preparation methods of sulfides.The paper uses nickel-cobalt as the metal source,urea as the alkali source,sodium sulfide as the vulcanizing agent and other raw materials.The composite electrode material with nano-nickel-cobalt sulfide(NiCo2S4)as the shell and activated carbon fiber/graphene as the core was prepared by hydrothermal method.The morphology and composition were analyzed by field emission scanning electron microscopy(SEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and transmission electron microscopy(TEM).The composite material was used as an electrode material to form an electrode sheet,and its electrochemical performance was analyzed by cyclic voltammetry(CV),galvanostatic charge-discharge(GCD)and electrochemical impedance spectroscopy(EIS).The main contents of the paper are:1.The paper prepared the nickel-cobalt sulfide by hydrothermal method,room temperature vulcanization method and annealing three-step method.The product was characterized by XRD and SEM by controlling the reaction process.The results verified the feasibility of the room temperature vulcanization method.The material was tested for electrochemical performance,including CV,GCD,EIS,and cyclic charge and discharge tests.The electrochemical test results show that the current density is 0.5 A g-1,1 A g-1,2 A g-1,3 A g-1,4 A g-1,5 A g-1,10 A g-1.Under the condition of 1 A g-1,the mass specific capacitance of the single electrode is 780 F g-1,744 F g-1,688 F g-1,642 F g-1,600 F g-1,580 F g-1,460 F g-1,which exhibits a high capacitance,retains 98%of the original specific capacitance after 5,000 cycles of charge and discharge testing.2.In order to improve the low conductivity of nickel-cobalt sulfide and improve the electrochemical performance,composite electrode materials(ACF/NiCo2S4 and rGO/NiCo2S4)with core-shell structure were prepared by using activated carbon fiber and graphene as substrates,respectively.The formed electrode materials have three-dimensional and two-dimensional structures,respectively,and the morphology is uniform,and the three-electrode performance tests are performed on these mater:ials.The results show that both exhibit excellent single electrode performance.The mass ratio capacitance of ACF/NiCo2S4 and rGO/NiCo2S4 were 1682 F g-1 and 1080 F g-1 at a current density of 1 A g-1 respectively.To further evaluate the practical performance of these materials,they were assembled into hybrid supercapacitors ACF/NiCo2S4//ACF and rGO/NiCo2S4//ACF,and their electrochemical properties were tested.ACF/NiCo2S4//ACF has an energy density of 49.38 Wh kg-1 at a power density of 800 W kg-1,up to 82.88%cycle stability after 5000 cyclic test,and rGO/NiCo2S4//ACF at a power density of 400 W kg-1,the energy density is 74.78 Wh kg-1,and after cycling for 3000 cycles,the specific capacitance is maintained at 88.7%.