Modification Of V₂O₅ Cathode Materials For Lithium-ion Batteries

With the development and application of nanotechnology,V₂O₅ with layered structure has attracted more and more attention due to its advantages of high theoretical capacity,low cost and abundant sources,which can be used as cathode material for new generation lithium-ion batteries.However,its commercialization process has be largely hindered by its low lithium-ion diffusion coefficient,low conductivity and poor structural stability.Therefore,it is great significance to explore the modification of V₂O₅.In this paper,carbon-based V₂O₅ nanorods were synthesized by hydrothermal method and chemical impregnation method.V₂O₅ nanoparticles were directly grown on foamed nickel-based by a facile hydrothermal process.Meanwhile,their morphology,structure,composition,pore property and electrochemical properties were investigated systemly.The pure V₂O₅ nanorods are stacked by numerous V₂O₅ nanoparticles,which synthesized by hydrothermal method.The V₂O₅ nanorods can be anchored to the surface of carbon microspheres by coordinating the oxygen-containing functional groups with the element of V in V₂O₅,and thus prohibit the agglomeration of the V₂O₅nanorods.It not only retains a large specific surface area of the carbon-based V₂O₅nanorods materials and increases the soak of electrolyte,but also exposes more reactive sites,as well as increases the conductivity of the active materials.The research indicates that the initial discharge specific capacity of V₂O₅ nanorods electrode increases first and then decreases with the increasement of the concentration of NH₄VO₃ and hydrothermal time.The optimal concentration and hydrothermal time are0.071 mol/L and 12 h,respectively.At the same time,the initial discharge specific capacity of carbon-based V₂O₅ nanorods also shows a trend of increase first and then decrease with the increasement of the ratio of V₂O₅ and the calcination temperature of carbon microspheres.Under the optimal conditions of mass ratio of 8:1 and calcination temperature of carbon microspheres at 1100°C,it shows an initial discharge specific capacity of 270 mAh/g can be achieved.After 50 cycles,the capacity retention is as high as 82.9%.Meanwhile,the corresponding discharge specific capacity is able still to maintain at 171 mAh/g at the current density of 2000 mA/g,which suggesting the carbon-based V₂O₅ nanorods possess excellent rate performance and electrochemical performance.The cathode for lithium-ion battery was fabricated by hydrothermal growth of V₂O₅ nanoparticles directly on the nickel-foam substrate.The 3D network structure of nickel-foam substrate not only can increase the electron transport channel,but also can be directly assembled into the battery as a current collector.It avoids the use of the conductive agents and binders,which increase the loading of the active materials.Moreover,the process of electrode fabrication is also simplified significantly.The results show that the discharge specific capacity of foamed nickel-based V₂O₅ electrode increases first and then decreases with the increasement of hydrothermal time and temperature.The foamed nickel-based V₂O₅ nanoparticles electrod exhibits an optimal electrochemical activity,which is fabricated under 170°C and 3 h.At a small current density of 100 mA/g,the initial discharge specific capacity is 277 mAh/g.After 50cycles,the capacity retention is 54.2%.With the increase of current density,the discharge specific capacity is gradually reduced.When the current density come backed to a low current density,its discharge specific capacity retention rate is as high as92.7%.In summary,when used as a cathode electrode material for lithium-ion batteries,the carbon-based V₂O₅ nanorods electrode exhibits high capacity,good cycle stability and excellent rate performance.However,the foamed nickel-based V₂O₅ nanoparticles electrode can provide a higher discharge specific capacity at a low current density.