Research On Construction And Energy Storage Of V₂O₅ Composite Materials

With the deeper understanding of the world,the harmonious coexistence of man and nature has been paid attention by more and more people.On the environmental and energy problems faced currently are also known newly.In order to solve these problems,many researchers have set their sights on renewable clean energy.The large-scale use of secondary energy such as solar energy,wind energy,and geothermal energy will be inseparable from energy storage equipment.As electrochemical energy storage equipment,batteries and supercapacitors have become the current focus of research.The realization of high-performance electrochemical energy storage equipment is mainly limited by electrode performance.Transition metal oxides have entered gradually the human field of vision.Among them,vanadium pentoxide（V₂O₅）provides the possibility for the development of electrochemical energy storage devices,owing to variety changeable valence states,special layered structure and high theoretical specific capacity.However,the wide application of vanadium pentoxide in electrochemical energy storage devices is limited by the poor conductivity and unstable structure.In this paper,with complexly modified vanadium pentoxide,the electrochemical performance will be improved and application in the field of energy storage promoted.The main research work is as follows:（1）The self-supporting electrode of V₂O₅@carbon cloth has been prepared by solvothermal method.The optimal preparation conditions have been determined,namely,the solvothermal time is 12 hours,and the concentration of V₂O₅ is 0.0125 mol L^-1.The V₂O₅@carbon cloth electrode prepared under the optimal conditions was complexed with a single-layer reduced graphene oxide（r GO）to form a r GO@V₂O₅@carbon cloth self-supporting electrode.Because of the complex of r GO with V₂O₅@carbon cloth,the specific surface of the electrode active material and the contact area with the electrolyte are increased,the conductivity of the electrode is improved,the volume change of the electrode material during the charge and discharge process is also effectively buffered.When the r GO@V₂O₅@carbon cloth self-supporting electrode and lithium were assembled into a lithium-ion battery,the discharge specific capacity can reach 309 m Ah g^-1 in the first cycle and the capacity retention rate is 80.9%after 80 cycles under the current density of 100m A g^-1.（2）Honeycomb-like Yb-doped V₂O₅·n H₂O binder-free thin film electrodes has been synthesized via a simple and convenient sol-gel method.Thin-layer honeycomb-like morphology formed by the introduction of Yb³⁺into the V₂O₅·n H₂O,which promotes markedly the electrochemical performance of V₂O₅·n H₂O thin film electrode.After the condition optimization,the 8%Yb-V₂O₅·n H₂O exhibits superior electrochemical performance with specific capacitance of 703 F g^-1(at 1 A g^-1)and outstanding cycling stability.Besides,owing to the ultra-high conductivity of oxide super-P（OSP）nanoparticles,the V₂O₅·n H₂O@OSP-4 binder-free film electrode shows also high specific capacitance of 627 F g^-1,which prepared by the same simple sol-gel strategy.The assembled 8%V₂O₅·n H₂O//V₂O₅·n H₂O@OSP-4 device delivers a high specific energy density and excellent cycling stability（93%capacitance retention after2000 cycles）.