Synthesis And Electrochemical Performance Study Of Nickel-Based Three-dimensional Electrode Materials

With the continuous development of the economy,the increasing consumption and demand of petroleum resources by mankind will inevitably cause the depletion of oil resources and the deterioration of the environment.The research and development of high-efficiency electrochemical energy storage devices become more and more urgent due to the increasing energy demand.Sodium-nickel chloride and lithium ion secondary batteries as the main devices of the electrochemical energy storage system are playing an important role in solving current environmental pollution and energy crisis.As the key of the electrochemical energy storage device,the electrode material has an important influence on the energy density and the cycle performance of the energy storage devices.Nickel and nickel-based compounds have the advantages of easy mass preparation,low cost,and outstanding electrochemical performance.Therefore,the development of nickel and nickel-based metal compounds is of great significance for electrochemical energy storage system.This dissertation mainly focuses on the design of nanostructured,composited and heteroatom doped nickel and nickel-based compounds,aiming to improve the electrochemical performance of the sodium-nickel chloride and lithium ion batteries.The details of the dissertation are summarized as follows:（1）The preparation and electrochemical performance of three-dimensional Ni nanowire conductive network.In the positive electrode of sodium-nickel chloride batteries,due to the strong corrosiveness of the second electrolyte NaAlCl₄,the metal material used as the conductive network is easily corroded to increase the resistances of the battery,causing the battery performance to deteriorate,and even causing the battery to fail.Aiming to solve the above problems,three-dimensional Ni nanowires and carbon-coated Ni nanowire conductive network electrodes with strong corrosion resistance are designed in this dissertation.These materials can restrain the growth of nickel particles and alleviate the volume effect during the cycling,therefore the positive conducting network of Ni nanowires can be kept stable,and lead to better cycle performance of the battery.（2）The preparation and electrochemical performance of the reduced graphene oxide supported nickel sulfide nanotubes.From the perspective of simple and rapid preparation of nanostructured nickel sulfide electrodes,Na₂S and graphite oxide were added to the synthesized Ni nanowires.By controlling the reaction temperature and time,the free-standing electrode of the reduced graphene oxide supported nickel sulfide nanotubes was synthesized.（donated as Ni₃S₂@Ni NTs-rGO）.Two-dimensional reduced graphene oxide and one-dimensional Ni₃S₂@Ni nanotubes construct the three-dimensional,open and free-standing electrode.And their tight connection and interaction have a significant impact on the improvement of electrochemical performance.When the prepared composite is used as a free-binder and free-conductive agent electrodes of lithium ion batteries,it has a high specific capacity and excellent cycling performance.（3）The preparation and electrochemical performance of three-dimensional（3D）Ni₃S₂ nanosheets array.A 3D self-supported Ni₃S₂ nanosheet array was synthesized by a simple and environmentally solvothermal method.The electrode with the 3D self-supported Ni₃S₂ nanosheet array exhibits excellent electrochemical cycling performance.The reversible specific capacity can maintain at¹200 mA h g^-1 after1000 cycles at a current density of 0.5 A g^-1.Meanwhile,the specific capacity of 505mA h g^-1 can be achieved at a high current density of 8 A g^-1.The above results indicate that the uniform morphology,high specific surface area,and three-dimensional self-supported structure play an important role in improving the electrochemical performance of the electrode materials.（4）The preparation and electrochemical performance of multifunctional Ni₂P/Ni₃S₂ heterostructures and their superstructure.We demonstrate a simple and effective method to construct Ni₂P/Ni₃S₂ heterostructures and control their assembly into a superstructure（denoted as HT-NPS@C）at the nanoscale.The design of sulfur-doped nickel phosphide core-shell structure gives them rich active sites and high specific surface area,which greatly improves the lithium storage and sodium storage properties.Precisely constructing the carbon-coated Ni₂P/Ni₃S₂ heterostructures and their assembly into a three-dimensional（3D）superstructure can not only fast the transport kinetics in the crystal structures but also preserve the nanocrystals structures during the discharge and charge process,thereby obtaining excellent electrochemical performance.