Preparation And Electrochemical Performance Of Oxygen Vacancies On The Surface Of TiO2 Hollow Spheres

The development of new energy has become one of the main research objects of China's economic sustainable development.Generally,the utilization of new energy is mainly to convert it into electric energy for storage.TiO₂ energy storage materials with the characteristics of safe lithium potential,high specific capacity,good cycle performance and good rate performance have become one of the main research directions.However,the poor electronic conductivity and low diffusion coefficient of TiO₂ will limit its application in lithium-ion batteries.On the research surface,the introduction of oxygen vacancy and other defects in the preparation of TiO₂ can significantly reduce the resistance of TiO₂ lithium-ion batteries and improve their electronic and ion diffusion coefficients.However,up to now,the effect of oxygen vacancy on the mesoporous TiO₂ nano hollow spheres is still not obvious,and more researches only focus on the photoelectric properties of mesoporous TiO₂ nano hollow spheres.The application and research of mesoporous TiO₂ nano hollow spheres containing oxygen vacancy in lithium battery are lack of systematicness,which seriously restricts the improvement and development of the performance of lithium anode materials.Therefore,in this study,the mesoporous TiO₂ nanospheres with oxygen vacancy are taken as the research object.Firstly,the polycrystalline TiO₂ with oxygen vacancy is established.Based on the adsorption energy,electronic density of state and work function,the influence of oxygen vacancy on the Li⁺storage performance and surface electronic structure of different crystalline TiO₂ is analyzed,and the effect of different oxygen vacancy concentration on the carrier concentration of anatase TiO₂ is discussed The influence of oxygen vacancy on the electronic structure and Li⁺diffusion of TiO₂surface is clarified theoretically.On this basis,mesoporous TiO₂ hollow spheres with different oxygen vacancy concentration were obtained by sintering in different temperature and oxygen deficient atmosphere,and the electrochemical properties of mesoporous TiO₂ hollow spheres with different oxygen vacancy concentration were tested.After that,in order to make the oxygen vacancy exist stably on the mesoporous TiO₂ hollow nanospheres for a long time,different concentrations of Cu²⁺were doped,and the electrochemical synergistic effect of Cu²⁺and oxygen vacancy was revealed.The conclusions are as follows:(1)The calculation based on the first principle shows that oxygen vacancy is more easily formed on the surface of anatase TiO₂ under the same conditions.In the process of electrochemical cycle,the proper amount of oxygen vacancy can make anatase TiO₂reduce its Li+transport barrier and electron hole distance,and increase the carrier concentration in it to the greatest extent,so that its electron/ion conductivity can be improved.(2)In order to verify the effect of oxygen vacancy on the electrochemical properties of anatase TiO₂,mesoporous TiO₂ hollow spheres with different concentration of oxygen vacancy were prepared at different sintering temperatures.Through different sintering temperature,the surface of mesoporous TiO₂ hollow spheres can generate different concentration of oxygen vacancy,and the concentration of oxygen vacancy increases with the increase of sintering temperature.Through the electrochemical performance characterization,it can be found that when the molar ratio of Ti³⁺/Ti⁴⁺reaches 0.348,the sample shows good electrochemical synergy,the discharge specific capacity and conductivity performance are greatly improved,and the appropriate oxygen vacancy concentration adds mesoporous TiO₂ nano hollow sphere lithium ion and electronic diffusion channel,greatly reducing the band gap value and Li+diffusion barrier of anatase TiO₂,maximizing the limit The ionic conductivity and electronic conductivity of the mesoporous TiO₂ hollow nanospheres were enhanced by the addition of.(3)In order to stabilize the oxygen vacancy on the surface of the mesoporous TiO₂ nanospheres,Cu²⁺was doped into the surface of the mesoporous TiO₂nanospheres.The phase detection results show that the low valence Cu²⁺will replace the high valence Ti⁴⁺in the octahedral gap after doping TiO₂.In order to ensure the charge balance,oxygen holes will be formed on the surface of mesoporous TiO₂ hollow nanospheres.Through electrochemical characterization,it can be found that Cu²⁺expands the lattice volume of TiO₂ after doping into the surface of the mesoporous TiO₂ nanospheres,thus providing a wider diffusion path for Li⁺diffusion,reducing its diffusion barrier,and improving the electrochemical activity of the surface of the mesoporous TiO₂ nanospheres.Moreover,the existence of oxygen vacancy can also improve its electrochemical performance.