Preparation Of Transition Metal Oxide Anode Materials For Lithium Storage Application

Countries in the world have invested a lot of money to develop and use clean energy in response to the energy crisis and environmental pollution.For this reason,the development and utilization of energy storage devices have always been in the hot direction.The representative lithium-ion battery is used in all aspects of people's daily life because of its advantages such as Long cycle life,high energy density,green safety.However,people's requirements for lithium-ion batteries are becoming higher and higher.Graphite anode materials used in lithium-ion batteries for more than 20 years have become the shortcomings of lithium-ion battery performance because of their low theoretical specific capacity?372 mAh/g?.Therefore,there is an urgent need for anode materials with high specific capacity to replace graphite.As a representative of anode materials with high theoretical specific capacity:Si?theoretical specific capacity 4200mAh/g?and transition metal oxide?Theoretical specific capacity¹000 mAh/g?has become a research hotspot in recent years.But these materials have a large volume expansion rate during charge and discharge,which leads to a significant reduction in the reversible capacity of the battery.In order to buffer their volume expansion,we tried to use the cumulative effect of the composite material,unique microstructure to improve the electrochemical performance of Si and transition metal oxide.The main research contents are as follows:Preparation of Si@TiO₂ nanofiber anode material by electrostatic spinning.The optimal preparation process was obtained.The influence of silicon powder addition amount and heat treatment process parameters on the samples was discussed.At a current density of 100 mA/g,the initial discharge specific capacity of the sample reached 3359 mAh/g,and it remained stable at 392 mAh/g after 200 cycles.Compared with the pure nano silicon powder anode material,the cycle performance has been greatly improved.TiO₂ nanofibers were prepared by electrospinning method,the influence of heat treatment process parameters on its microscopic morphology was studied,and the optimal heat treatment process of TiO2 nanofibers with excellent morphology was obtained:heat treatment temperature 500?,heating rate 1?/min,heat preservation 1h.Fe₂O₃@TiO₂ nanofiber anode material was prepared by solvothermal.By optimizing the preparation process,Fe₂O₃ nanoparticles were loaded on the surface of TiO₂ nanofibers.Its unique morphological structure improved the reversible capacity and rate performance of Fe₂O₃.At a current density of 100 mA/g,the initial discharge specific capacity of the sample reached 1352 mAh/g,and it remained stable at 330mAh/g after 200 cycles.At a high rate current density of 2C,the reversible capacity is71 mAh/g.Preparation of CoFe₂O₄@TiO₂ nanofiber anode material by solvothermal.By controlling the preparation process parameters,samples with optimal morphology and electrochemical performance were obtained.At the current density 100 mA/g,the initial discharge specific capacity of the nanofiber anode material reached 1489 mAh/g.After200 charge-discharge cycles,the reversible capacity stabilized at 355 mAh/g,and at a high-rate current density of 2 C,the reversible capacity was 102 mAh/g.