Synthesis And Electrochemical Performance Of Nb₂O₅ And Nb₂O₅-based Composites

3C products,electric cars,flexible wearable devices,and energy storage devices have raised challenges for the charging speed and calendar life of anode materials for lithium-ion batteries.The development of materials that can work stably at high current densities and can work for a longer time is still a challenge for researchers.The low conductivity of Nb₂O₅ lead to the slow electrochemical reaction kinetics which is unfavorable to its high rate performance and the specific capacity of Nb₂O₅ anodes still need to be improved.Materials of Nb₂O₅ with special nanostructure and morphology were designed and composites with Carbon are constructed to improve the transportion of lithium-ion,thus ameliorateing the electrochemical properties.The research includes the following three aspects:1)One-dimensional Nb₂O₅ nanorods were synthesized by hydrothermal method and applied for anode materials in lithium ion batteries.Solid Nb₂O₅ nanorods are obtained when surfactant P123 was only utilized in the hydrothermal process,while Nb₂O₅ nanorods were pregnant with regular cuboid-shaped boxes and pillars at both the center and the ends when P123 and CTAB surfactants were incorporated.Box-implanted Nb₂O₅?BI-Nb₂O₅?nanorods exhibit a high reversible capacity of 237.6 mA·h/g cycled at the current density of 40 mA/g after200 cycles and a remarkable rate capacity of 119.5 mA·h/g at the current density of 5000 mA/g.Their outstanding rate capability can be attributed to regular boxes implanted in Nb₂O₅ nanorods,which can provide fast transportation path for lithium ions and electronics and relieve the volume change in charge and discharge process.2)Uniform Nb₂O₅ nanospheres/surface-modified grapheme?SMG?composites for anode materials in lithium ion batteries were synthesized by hydrothermal method.The microstructure and morphology of composites were investigated by X-ray diffraction,scanning electron microscopy and transmission electron microscope techniques.The experimental results showed that Nb₂O₅ nanospheres were tightly and uniformly grown on the surface of SMG nanosheets.Spheres with nano-size can shorten the distance of the reaction sites from the lithium-ion,and the intimate contacts between Nb₂O₅ and graphene enhance the conductivity and acive sites of electrochemical eaction.Nb₂O₅ nanospheres/SMG composites exhibited an impressive reversible capacity of 404.6 mA·h/g at the current density of 40 mA/g after 100cycles,and an excellent rate capacity of 345.5 mA·h/g at the current density of 400 mA/g.3)TO equip both the pore strcuture and high electronic conductivity,uniform nanocable-like Nb₂O₅/surface-modified carbon nanotubes?SMCNTs?composites for anode materials in lithium ion batteries were synthesized by hydrothermal method.It was indicated that Nb₂O₅nanosheets were tightly and uniformly cultivated on carbon nanotubes when CNTs were pretreated with concentrated H₂SO₄.As a result,Nb₂O₅/SMCNTs composite materials showed remarkable electrochemical performance as anode materials for lithium-ion batteries.It delivered a high reversible capacity of 441 mA·h/g cycled at the current density of 40mA/g after 100 cycles and an excellent rate capacity of 185 mA·h/g at the high current density of 5000 mA/g after 200 cycles.