Study On Preparation And Its Zinc-ion Batteries Performance Of Vanadium Oxide Electrode Material

In recent years,due to the over-exploitation of coal and other fossil energy,environmental problems have become increasingly serious.Renewable clean energy such as solar energy,wind energy and tidal energy has been vigorously developed.The research and development of more efficient energy storage media has become a current hotspot.Among them,aqueous zinc-ion batteries have become the most promising secondary battery system to replace lithium batteries due to their high safety,low cost,high capacity,and high energy density.Among its cathode materials,vanadium based materials have attracted extensive attention due to their advantages of high theoretical capacity,low cost,abundant resources,multivalence state,reversible capacity and rate performance.However,the problems of vanadium based materials such as poor electrical conductivity,easy dissolution of anode materials and poor cycle stability limit their further development.In order to improve the performance of vanadium oxide batteries,many effective strategies have been proposed,such as optimizing the material structure,constructing the composite structure,pre-insertion strategy,adjusting the interlayer water and so on.The results show that the utilization rate and electronic conductivity of active sites on vanadium matrix materials can be effectively improved by pre-insertion transition metal ions,adjusting the layer spacing of vanadium based materials through column effect,and generating lattice distortion and introduce defects in the host material.Meanwhile,the introduction of transition metal ions is usually accompanied by the introduction of structural water.The synergistic effect of structural water and foreign cations ensures the stability and opening of the cathode structure,thus enhancing its electrochemical energy.Up to now,most of the methods for pre-intercalating ions are traditional hydrothermal synthesis,which requires strict equipment and takes a long time,more convenient and faster methods are still lacking in reports.The electronic structure of transition metal ions has the advantage of being tunable,and it is an effective optimization method to introduce transition metal ions into V2O5 materials to optimize its electronic structure.However,except the intrinsic crystal structure,the morphology of the material also greatly affects the rate capability of the material.Among them,the two-dimensional layered structure can provide a shorter ion/electron diffusion length to improve the rate capability.The construction of two-dimensional layered vanadium-oxygen material with mixed valence state is helpful not only to improve the conductivity of the material,but also to obtain faster ionic diffusion kinetics.In this work,the structure of vanadium based materials is optimized by pre-intercalating transition metal ions and constructing layered vanadium oxides with mixed valence states.The main research contents are as follows:(1)Preparation of transition metal ion-doped V2O5·3H2O and its performance of aqueous zinc-ion batteries:V2O5·3H2O nanosheets doped with different metal ions were prepared by adding transition metal ions such as Cu2+、Fe2+、Co2+and Ni2+ into ammonium metavanadate solution by simple and rapid precipitation method.The samples were characterized by XRD.SEM,HRTEM and XPS to explore the effect of different transition metal ions on the performance of V2O5·3H2O battery.The results show that the doping of Ni2+ enlarges the interlayer spacing of the material,increases the diffusion rate of Zn2+,makes the crystal structure of V2O5·3H2O more stable.The effect of different transition metal ions on the performance of V2O5·3H2O battery was investigated.The results show that when the molar ratio of V/Ni in the reactants is 7:1,the synthesized V2O5·3H2O(Ni-VO-1:7)has the best electrochemical performance.When the current density is 0.1 A g-1,the initial specific capacity is 458 mAh g-1,which is higher than most of the reported vanadium oxides.After 2000 cycles,there is still a capacity retention rate of 94.2%,showing excellent cycle stability.(2)Design and preparation of mixed-valence V10O24·12H2O ultrathin nanosheets and their performance in zinc ion batteries:At room temperature,V10O24·12H2O ultrathin nanosheets with mixed valence states were prepared by solution-gel method using the gel formed by V2O5 and hydrogen peroxide as the precursor solution through adding vanadium sheets.The study shows that adding vanadium flakes into vanadic acid sol is the key to synthesizeV10O24·12H2O.The construction of the mixed valence states and the synergistic effect between water molecules provide a large number of active sites for the de-intercalation of Zn ions,which facilitates the transfer of electrons and Zn2+,resulting in excellent electrochemical performance.The effects of the amount of V2O5 on the morphology and performance of V10O24·12H2O was investigated,and the optimal concentration of reactant was determined.The results showed that the electrochemical performance of V10O24·12H2O-0.5 was the best when V2O5 was 0.5 mmol.When the current density is 0.1 A g-l,the specific discharge capacity can reach 395 mAh g-1,and after 5500 cycles,the capacity retention rate is 90.3%，showing excellent cycling stability.