Synthesis And Energy Storage Applications Of ?A-?A Group Metallic Compounds Anode Materials

In the context of the massive consumption of global petrochemical resources,the worrying reserves,and the gradual expansion of the scale of energy storage systems,the development of high-performance energy storage batteries is the only way to promote the development of new energy.As an important part of the energy storage,the anode material's working voltage,specific capacity,and structural stability directly affect the performance of the battery.However,simple selenide and telluride nanoelectrodes are easy to agglomerate,and the electrode structure is easy to be destroyed in the process of charge and discharge,leading to the reduction of specific surface area and the loss of active site,which prevents them from using their full capacity.Metal oxide(MO),metal sulfide(MS)and metal selenide(MSe)have gradually developed into new anode materials due to their high capacity and abundant reserves.However,simple metal chalcogenide electrodes are prone to agglomeration,and the electrode structure is easily destroyed,resulting in a decrease in specific surface area and active sites,which seriously hinders the increase in its actual capacity.In this thesis,the high energy density V-VIA group metal compounds(Bi₂Se₃,Sb₂Te₃)based on transformation,intercalation and alloying reactions are investigated.Electrospinning is used to prepare Bi₂Se₃ carbon-based composite electrodes with a certain degree of flexibility to solve the easy agglomeration of nanoparticles.r GO@Bi₂Se₃@CC electrode to solve the structure is easy to be destroyed.Sb₂Te₃-Te heterojunction electrode to combine the advantages of 1D and 2D nanomaterials and improve the conductivity and diffusion coefficient.The main research results are as follows:(1)The three-dimensional network structure Bi₂Se₃/CNFs flexible electrode was prepared by electrospinning combined with selenization in ampoule tubing.The results showed that particles of 40 nm were embedded in CNFs with diameter of 400 nm.A large number of carbon nanofibers form a three-dimensional network structure,which fully combines the high specific capacity of Bi2Se3 and the conductivity of carbon,and the carbon fiber membrane has a certain degree of flexibility,which expands its application in the field of flexible electrodes.The unique material structure not only improves the conductivity of the pure Bi₂Se₃ electrode,but also effectively inhibits the agglomeration of nanoparticles,which greatly improves the cycle stability of the electrode.When the Bi₂Se₃/CNFs flexible self-supporting electrode is used as the negative electrode of a lithium/sodium ion battery,the specific capacities are 443 and 387 m Ah g^-1,respectively.(2)The Bi₂Se₃ nanosheets array was synthesized on the surface of a flexible carbon cloth by vapor deposition method,and a layer of graphene oxide was coated on the surface of the nanosheet,and r GO@Bi₂Se₃@CC was obtained by reduction.The length of Bi₂Se₃nanosheets is about 200 nm,and the thickness is about 5 nm.A large number of Bi₂Se₃nanosheets form an array and grow on the surface of flexible carbon cloth,providing a large number of active sites.The reduced graphene oxide coated on the surface of the Bi₂Se₃nanosheets improves the conductivity,structural integrity and stability of the electrode,and can effectively avoid serious structural collapse and has excellent cycle performance.When used in lithium ion battery,the specific capacity is 484 m Ah g^-1,and the flexible carbon cloth substrate gives the r GO@Bi₂Se₃@CC electrode excellent flexibility.(3)A solvothermal method was used to synthesize the Sb₂Te₃-Te multi-level nanoheterostructure consisting of one-dimensional Te nanowires strung parallel two-dimensional Sb₂Te₃ nanosheets.The length of the Te nanowire is about 6?m,the thickness of the Sb₂Te₃ nanosheet is about 25 nm,and each Sb₂Te₃ nanosheet forms a T-shaped nano heterojunction with the Te nanowire.The space between adjacent nanosheets has a buffer and protection effect on the structure,and can inhibit the agglomeration of active materials.The one-dimensional nanowire allows the electrolyte to rapidly diffuse into the internal area,thereby increasing the cycle life.1D and 2D nano-heterostructures with different band gaps have quantum effects,high mobility and unique spatial structure,which promote the electron conduction and Na⁺diffusion based on the built-in electric field of the Sb₂Te₃-Te nano-heterojunction.The specific capacity of Sb₂Te₃-Te nanoheterojunction electrode in sodium ion battery is 365 m Ah g^-1.