Study On The Design,Performance And Lithium Storage Behavior Of Vanadium Base Alkali Metal Ion Battery Composite Electrode

With the widespread application of energy,human society has developed rapidly,but now it is facing the problems of energy depletion and environmental pollution.Therefore,renewable energy is an important direction for future development,and secondary batteries are an important way to store and convert energy.Developing lithium ion batteries with low cost,high safety,and high energy density has become a research hotspot in recent years.Due to the advantages of high theoretical specific capacity,vanadium pentoxide is expected to become a new negative electrode material for lithium ion batteries,with good development prospects.However,in the application of vanadium pentoxide in lithium ion batteries,its low electron mobility leads to poor electrical conductivity,and there is a problem of poor cycle stability during overcharging.In order to improve its disadvantages,this paper introduces carbon materials with good electrical conductivity and titanium dioxide with excellent cycle stability to composite with vanadium pentoxide to give play to the synergy of the three advantages.The main content of this article includes:（1）V₂O₅/C nanocomposite fibers were prepared by electrospinning.The effect of different carbonization temperature on the morphology of nanocomposite fibers was studied.SEM showed that the surface of V₂O₅/C nanocomposite fiber was rough,and the diameter of V₂O₅/C nanocomposite fiber became smaller and smaller with the increase of carbonization temperature.Through the electrochemical performance test of V₂O₅/C nanocomposite fiber,it was found that the specific discharge capacity of V₂O₅/C nanocomposite fiber with carbonization temperature of 500℃was 604.2 m Ah·g^-1 after150 cycles at the current density of 0.1 A·g^-1,which was much higher than that of V₂O₅/C nanocomposite fiber with carbonization temperature of 400℃and 600℃and single V₂O₅,with good cycle stability.Electrochemical impedance spectroscopy showed that the charge transfer impedance of V₂O₅/C nanocomposite fiber was lower than that of single V₂O₅,and the composite of amorphous carbon improved the conductivity of the material.The synergistic effect between V₂O₅ and carbon materials gives play to the advantages of high specific capacity of V₂O₅ and good conductivity of carbon materials,making V₂O₅/C nanocomposite fibers obtain excellent electrochemical properties.（2）V₂O₅/TiO₂ nanocomposite fibers were synthesized by electrospinning.The effects of different V/Timolar ratios on the morphology of nanocomposite fibers were studied.Through SEM,it was found that the continuity of V₂O₅/TiO₂ nanocomposite fiber with V/Timolar ratio of 1:1 was good,while the continuity of V₂O₅/TiO₂ nanocomposite fiber with V/Timolar ratio of 2:1 was poor.Through the electrochemical performance test of V₂O₅/TiO₂ nanocomposite fiber,it was found that the specific discharge capacity of the first ring of V₂O₅/TiO₂ nanocomposite fiber was smaller than that of the single V₂O₅,but much larger than that of TiO₂.The introduction of TiO₂ into V₂O₅ reduces the specific discharge capacity of its first cycle,but effectively improves its cycle stability.V₂O₅/TiO₂nanocomposite fiber has excellent cycle stability,but its capacity is low.It is still necessary to further study and prepare high-capacity nanocomposite fiber.（3）V₂O₅/TiO₂/C nanocomposite fibers were synthesized by electrospinning.The effect of different solution solubility on fiber morphology was studied.SEM observation showed that V₂O₅/TiO₂/C nanocomposites with a solution concentration of 10%exhibited uniform fibers and the best morphology.V₂O₅/TiO₂/C nanocomposite fibers with different V/Timolar ratios were prepared based on 10%solution concentration.Through SEM,it was found that the surface of V₂O₅/TiO₂/C nanocomposite fibers was relatively rough,and the fiber diameter was nano size.By testing the performance of V₂O₅/TiO₂/C nanocomposite fibers in lithium ion batteries,it was found that the composite nanofibers with a molar ratio of V/Tiof 2:1 had the best cycle stability and magnification performance,with a first cycle discharge specific capacity of 1322.1 m Ah·g^-1.After 150cycles at a current density of 0.1 A·g^-1,the discharge specific capacity reached 692.9m Ah·g^-1.After 40 cycles of charging and discharging at different current densities,it still has a specific discharge capacity of 818.7 m Ah·g^-1.