Preparation And Electrochemical Properties Of Nickel-Cobalt Based Electrode Materials By Electrospinning

Pollution from fossil fuels,growing demand for energy,and the harmful effects of carbon dioxide in the atmosphere are forcing the world to find alternative ways of generating and storing energy.Many scientists around the world are looking for different ways to produce and store energy.Solar and wind energy are sustainable sources of power generation,but they are not continuous and require storage facilities.Therefore,the development of high-energy and power-density batteries and hybrid supercapacitors is of great significance to supplement this energy storage demand.Due to their high power density(>10 k W kg^-1),excellent rate capability,extended and stable cycle life（>105 cycles）and eco-friendly.Supercapacitors have been applied to prominent energy storage platforms such as electronic communications,aerospace,and power transportation.Although supercapacitors have been proven to be a reliable source of energy storage systems in theory and are used in various applications,their performance still needs to be further improved to meet the ever-expanding energy demand of modern society.As nickel-cobalt compounds have the advantages of high theoretical capacity,high reserves,and low prices,the main work of this thesis is to study nickel-cobalt compounds（NiCo₂O₄/NiCo₂S₄）combining high-voltage electrospinning technology,and further conduct a reduction process on the basis of sulfides.New nanotube materials with unique morphology have been designed and prepared,then their structure and electrochemical performance performance was analyzed.The main content of the work is as follows:Based on surfactants modified PAN nanofibers,NiCo₂O₄ nanotube materials can be prepared and employed as electrode materials for supercapacitors.Using the PAN fiber produced by electrospinning as a template,the c-NiCo₂O₄ material is obtained through simple and environmentally friendly hydrothermal,etching and thermal decomposition processes.At a current density of 1 A g^-1,the specific capacitance is 171.5 F g^-1.And at a high current density,the capacitance loss rate after2000 cycles is only 13.09%.At the same time,the rate performance of c-NiCo₂O₄（73.2%）is much higher than that of NiCo₂O₄（47.8%）.The addition of CTAB provides a direction for the preparation of high-performance sulfide materials.On the basis of the nickel-cobalt oxide,the hierarchical NiCo₂S₄-based nanotube material was successfully synthesized by a combination of vulcanization and reduction treatment,which was directly used as an electrode material and showed excellent electrochemical performance.The addition of CATB in the electrospinning process makes the c-NiCo₂S₄ material show a completely different morphology from that of NiCo₂S₄ nanotubes.Compared with c-NiCo₂S₄,the rate performance and cycle stability of the Vc-NiCo₂S₄ electrode material are significantly improved due to the introduction of sufide vacancies.The comparison of electrochemical performance shows that the Vc-NiCo₂S₄ material has the best performance.The material exhibits excellent electrochemical performance at a current density of 1 A g^-1,and the capacitance retention rate reaches 65.8%at a current density of 10 A g^-1.In addition,it still has good capacitance retention and coulomb efficiency after 2000 cycles at high current density.When the power density of the assembled Vc-NiCo₂S₄//Vc-NiCo₂S₄supercapacitor is 260 W kg^-1,the maximum energy density is 31.8 Wh kg^-1.