Study Of Synthesis And Lithium Storage Behavior Of Niobium Based Oxides

In rencent years,through the rapid development of electric vehicles and 3 C digital products,people have put forward higher requirements for power performance and safety performance of lithium-ion batteries.Traditional graphite anodes and silicon anodes that have gradually matured in recent years will result in SEI films and lithium dendrites due to their low lithium ion intercalation and deintercalation potentials.Therefore,materials such as lithium titanate with high intercalation and deintercalation potential and high rate performance have been developed to meet the requirements of high power and high safety.However,the scant theoretical capacity of lithium titanate limits its further development.Thus,looking for an anode material with high capacity,high safety and high rate performance is the key field of current research on anode materials of lithium ion batteries.Niobium-based oxides are one of the hotspots of current research,because of their high intercalation and deintercalation potentials which can avoid the formation of SEI films and lithium dendrites.At the same time,some niobium-based oxides also have high theoretical capacity and excellent rate performance.The most studied niobium-based oxides are Nb2O5,Ti-Nb-O and W-Nb-O.However,niobium-based oxides generally have the disadvantage of poor electronic conductivity,which will affect their electrochemical performance.In this paper,the preparation of WNb2O8 sub-micron rods,cobalt doping and carbon coating modification of Ti Nb2O7 sub-micron particles,and sub-micron spherical Ti Nb2O7 with porous hierarchical structure and oxygen vacancy modification were carried out on the study of niobium-based oxides.In this paper,WNb2O8 material with submicron rod structure was prepared by simple liquid phase method.Electron microscopy picture shows that the prepared rod-shaped material has a diameter between 100-200 nm and a length between 300-800 nm.This rodshaped structure is conducive to the rapid transmission of lithium ions inside the material.After a variety of spectroscopy testing methods,it was finally determined that the material's lattice structure belongs to the typical shear Re O3 configuration,which contains a large number of lithium ion channels.Its special microscopic morphology and lattice structure leading to an excellent rate performance.Even at 100 C,its specific capacity still reaches 81 m A h g-1.And the results of pseudocapacitance analysis show that the pseudocapacitance effect in the material occupies a very important position in the process of charging and discharging.In this paper,the Ti Nb2O7 submicron particles were prepared by simple liquid phase method and cobalt-doped and carbon-coated modified.After modifying the material with cobalt doping,it was found that when a small amount of cobalt is doped,the lattice structure of the material does not change significantly.However,when the doping amount is too large,the XRD results of the material show obvious changes,which indicates that a large amount of cobalt doping will damage the lattice structure of the material.Electrochemical test results show that cobalt doping can improve the cycling stability of the material,when it is doped with 1% cobalt,the stability of the material is improved from 68% to 82% after 100 cycles at 1 C rate.After carbon coating modification of the material,it was found that the peaks belonging to Ti O2 and Ti2Nb10O29 appeared in the XRD pattern of the material,which resulted in a large decrease in the capacity of the material.Finally,a porous hierarchical submicron spherical Ti Nb2O7 was synthesized and treated with H2/Ar atmosphere.The results show that the color of the materials will deepen with the increase of the treatment time of H2/Ar atmosphere.XPS results show that treatment with hydrogen and argon atmosphere will introduce oxygen vacancies into the material,and the concentration of oxygen vacancies will increase with the extension of the treatment time.Electrochemical test results show that the introduction of oxygen vacancies will reduce the polarization of the electrode,and improve the cycling stability and rate performance of the material.The hydrogen argon atmosphere treatment for 4 hours has a capacity of up to 140 m A h g-1 at 50 C rate,meanwhile,the capacity of the material without the hydrogen and argon atmosphere at this rate is only 37 m A h g-1.