Preparation Of Ion-intercalated Vanadium Oxide And Its Application In Aqueous Zinc Ion Batteries

Recently,"carbon peak"and"carbon-neutral"have frequently become popular words because of the rapid loss of non-renewable energy sources such as coal and the resulting environmental problems.Therefore,the country advocates vigorously developing clean energy such as wind and solar energy.However,these intermittent energy sources need to be converted into stable chemical energy before they can be fed into the smart grid.C urrently,lithium ion batteries（LIBs）are widely used as energy storage-level secondary batteries,but this causes rapid consumption of upstream lithium resources and increases the cost of lithium batteries.Therefore,it is urgent to find a new type of battery to replace LIBs in certain fields.Aqueous zinc ion batteries（ZIBs）have received widespread attention due to their high safety,low cost and other advantages.However,the cathode materials of ZIBs have many problems,such as the low capacity of Prussian blue analogues,the unstable structure of manganese-based materials and the prone to phase change.In order to cope with this situation,it is necessary to develop a vanadium-based cathode material with a stable structure and high capacity.However,common vanadium-based materials also have problems of varying degrees,such as vanadium dissolution and layer structure collapse.Therefore,in this paper,an ion-intercalated vanadium oxide was prepared by a chemical pre-intercalation method to stabilize the layer structure of vanadium oxide.The main research contents are as follows:（1）The（NH₄）₂V₆O₁₆·1.5H₂O（NVO）material was successfully prepared by microwave-assisted rapid hydrothermal reaction.X-ray diffraction（XRD）results show that NVO has good crystallinity and purity.Scanning electron microscope（SEM）and transmission electron microscope（TEM）photographs show that NVO is uniform nanowire morphology.The nitrogen isothermal adsorption-desorption test shows that the specific surface area of NVO is 45.2 m² g^-1.The electrochemical performance tests show that the prepared NVO electrode achieves fast Zn²⁺ion diffusion kinetics due to the large interlayer spacing,and can provide a high capacity of 145 mAh g^-1 even at a high current density of 8A g^-1.The ex-situ XRD and X-ray photoelectron spectroscopy in the first cycle confirmed the Zn²⁺ion intercalation mechanism of the NVO electrode.The intercalation of hydrated Zn²⁺ions and crystalline water molecules both act as pillars for the spacing of the supporting layers,so that the NVO nanowires are stable for a long time without rapid collapse.（2）The cationic ionic liquid（[BMIM]⁺）intercalated V₂O₅·nH₂O（BMIM-V₂O₅·nH₂O）and unintercalated V₂O₅·nH₂O were prepared by simple hydrothermal reaction,and they were used as the aqueous ZIBs cathode material.SEM images show that the morphologies of V₂O₅·nH₂O and BMIM-V₂O₅·nH₂O are bulk and nanobelt,respectively.XRD results show that the diffraction peaks of the two materials are similar,and the peak positions are slightly shifted.Performing performance tests on these two materials,the BMIM-V₂O₅·nH₂O electrode shows more excellent cyclic performance and rate performance.At a current density of 0.1 A g^-1,BMIM-V₂O₅·nH₂O shows a specific capacity of 447.2 mAh g^-1,which is higher than the 410.8 mAh g^-1 of V₂O₅·nH₂O.Even at 50 A g^-1,BMIM-V₂O₅·nH₂O can achieve a specific capacity of 155.6 mAh g^-1,and the capacity retention rate can reach 80.3%after 10000 cycles.