Synthesis And Electrochemical Properties Of Two-dimensional Nanocomposites Based On Polyphosphazene

As a renewable energy storage device,supercapacitor has excellent power density,fast charging and discharging,high cycle stability and so on.However,the energy density of its electrode materials is not high,limiting the development of supercapacitors.Therefore,the construction of an electrode material with outstanding performance is a key issue in the field of supercapacitor research.In recent years,in order to develop high-efficiency electrode materials to meet the growing demand of renewable energy storage system for high-performance electrode materials,a lot of research work has been carried out.Two-dimensional materials are widely used in the field of supercapacitors because of their large specific surface area,which facilitates full electrode-electrolyte contact and enables rapid charging and discharging.At present,the most exceptional two-dimensional materials are graphene,hexagonal boron nitride and molybdenum disulfide.Carbon material is the origin of electrode material,especially the carbon material doped with heteroatom is a new type of carbon material with great potential,which can provide additional channels for charge transfer.Polyphosphazene is a kind of high molecular polymer with abundant heteroatoms,and could be used as a precursor for preparing heteroatom-containing carbon materials.The synthesis of Fe₃O₄ is simple,and its theoretical specific capacity is relatively high,which makes it a hot topic.This work takes two-dimensional nanomaterials as the base material,polyphosphazene as the coating material,and Fe₃O₄ as the outermost composite material.The excellent properties of the three kinds of materials are organically combined by chemical methods,and the electrochemical properties of the composite material are improved by synergistic action.The main research contents are as follows:?1?Firstly,graphene?GO?was prepared by classical method,the polyphosphazene?PZS?and Fe₃O₄ were polymerized in situ on the surface of GO,then GO/PZS/Fe₃O₄ nanocomposites were prepared by carbonization at high temperature.The basic structure and properties were characterized by FTIR,XRD,XPS,SEM and TEM.Electrochemical performance tests showed that when the current density was 1 A g^-1,the specific capacity of the composite material was 183F g^-1,and it had a good stability.The capacity retention rate after 2000 cycles of charge and discharge was 70%,showing good electrochemical performance.?2?Two dimensional hexagonal boron nitride?h-BN?nanocomposites were prepared with boric acid and urea as raw materials,and then polyphosphazene?PZS?was polymerized in situ on the surface of h-BN nanocomposites to obtain h-BN/PZS nanocomposites;then Fe₃O₄ nanoparticles were synthesized in situ on the surface of h-BN/PZS/Fe₃O₄ nanocomposites were obtained.Finally,h-BN/PZS/Fe₃O₄nanocomposites were carbonized at high temperature,and their structures and properties were characterized.The samples were prepared into electrode materials and their electrochemical properties were tested.The h-BN/PZS/Fe₃O₄ electrode had a specific capacity up to 456 F g^-1 when the current density was 2 A g^-1.MnO₂//h-BN/PZS/Fe₃O₄ asymmetric supercapacitor was assembled with MnO₂ as positive electrode and h-BN/PZS/Fe₃O₄ as negative electrode.With the wide voltage window between 0-1.6 V and the current density was 0.5 A g^-1,the maximum specific capacity was 52 F g^-1.When the maximum power density is 6306 W kg^-1,the energy density is 5.3 Wh kg^-1.And it had good cycle stability(The retention rate of specific capacity was 64.8%after 2000 cycles of charging and discharging with the current density was 5 A g^-1).Comparing the electrochemical properties of h-BN,Fe₃O₄,and h-BN/PZS,h-BN/PZS/Fe₃O₄ composite exhibited more excellent electrochemical properties and could be used as a new two-dimensional nano electrode material in the field of supercapacitors.?3?A two-dimensional base material molybdenum disulfide?MoS₂?was synthesized by a hydrothermal method.Then polyphosphazene?PZS?was polymerized in situ on the surface of MoS₂.What's more,Fe₃O₄ nanoparticles were formed in situ on the surface of MoS₂.And finally,carbonized at high temperature to obtain two-dimensional MoS₂/PZS/Fe₃O₄ nanocomposites containing nitrogen,phosphorus and oxygen atoms.With the wide voltage window of-1.2-0 V and the current density was 2 A g^-1,the specific capacity was 403 F g^-1.The asymmetric supercapacitor MnO₂//MoS₂/PZS/Fe₃O₄ device was assembled.And the maximum capacitance was up to 73 F g^-1,when the power density was 6400 W kg^-1,the energy density was 10.7 Wh kg^-1.Furthermore,a LED was successfully lit after charging.Therefore,MoS₂/PZS/Fe₃O₄ nanocomposite is a very promising supercapacitor electrode material.