Preparation And Properties Of Cobalt Vanadium Oxide Based Energy Storage Materials

Lithium-ion batteries as an important part of the new energy field which are widely used in dayly life owing to its high working voltage,high specific gravity,large capacity,small self-discharge and good cycle performance.The commercial lithium anode material is graphite,and its theoretical specific capacity is 372mAhg^-1.The capacity is two low and can not be ignored.The theoretical specific capacity of silicon can reach 4200mAhg^-1 when it is used as an anode material for lithium ion batteries.But in practical applications,the capacity of silicon will be greatly attenuated due to the volume expansion.The researchers found that excessive metal oxides have great potential as lithium ion anode materials,such as:ZnO,Co₃O₄,MnO₂,MoO₂ and other single transition metal oxides,MnVO₃,MoV₂O₈,Co₃V₂O₈,and other multiple transition metal oxides.Both of the above transition metal oxides exhibit higher theoretical specific capacities?>1000 mAhg-1?.Among them,the current research hotspot is the cobalt and vanadium double metal oxides.Compared with other precious metal elements,cobalt and vanadium are rich in resource reserves and have unique electronic structures?more stable valence states?.Cobalt and vanadium oxides have changeable and regular micro-morphology,exhibit excellent electrochemical performance when used as lithium ion anode materials.It has a great application potential as a novel anode material for lithium ion batteries.Based on the above background,this paper mainly discussed the preparation of a variety of cobalt-vanadium double metal oxides that can be used as anode materials for high-performance lithium-ion batteries.The main works are as follows:?1?The synthesized micro-pencil Co₃V₂O₈?MPs-CVO?has a uniform microscopic size.By preparing the samples in different reaction stages and performing the corresponding SEM results,the growth process mechanism of MPs-CVO is obtained.After changing the Co/V ratio of the reaction material,the microscopic size of the product is gradually reduced,and the morphology of the sample is controlled to change from a micro-pencil to a hexagonal prism and irregular block,the final size is found to be at several hundred nanometers.The irregular block structure has the best electrochemical performance.By changing the alkaline concentration of the reactants,the synthesized MPs-CVO shows a structural state in which the bottom is inwardly depressed.?2?The rGO and MPs-CVO composites?rGO/CVO-MPs?were prepared by the composite method of MPs-CVO and graphene.Through the synergistic effect of surface-composite graphene and MPs-CVO,the conductivity of the substrate material is improved,the mechanical properties thereof are enhanced,and the morphology damage during charge and discharge is alleviated.The structure of the electrode material is protected to improve its electrochemical performance.It was found that the composite material exhibited about 25%higher specific capacity than pure MPs-CVO both at the current density of 200mAg^-1 or 1000mAg^-1.After a long cycle test,the performance of composite material is also much higher than MPs-CVO materials.?3?Microsphere solid Co₃V₂O₈?CVO MSs?were successfully prepared by hydrothermal reaction.In order to obtain its growth process,we collect reaction samples at different stages of the reaction,and perform SEM tests of the samples at different stages.Before the generation of CVO MSs,irregular block structure appeared,the hexagonal plate and the spherical coexistence,the gradually dissolved hexagonal plate and the spherical coexistence,and the complete CVO MSs were generated.The CVO MSs were tested for electrochemical performance.