Construction Of Nanostructured V₂O₅ Thin Films And Their Application In Electrochromic Device

Under the background of carbon peaking and carbon neutrality,green energy-saving building materials has attracted more attention.V₂O₅material,the only oxide material used as bipolar electrochromic material,has become a hot topic of research.The preparation of nanostructured V₂O₅films with excellent photoelectric properties is still a difficult challenge.In this paper,templating agents and hydrothermal methods were used to replicate sol-gel to construct nanostructured V₂O₅films.This paper focuses on the effect of annealing treatment on the structure and properties of V₂O₅films..provides a new idea for the efficient synthesis and application of nanostructured V₂O₅films.The template-assisted sol-gel method was used to prepare a 3DOM V₂O₅film on an ITO conductive glass substrate by covering a multi-layer PS colloidal sphere array,and then an annealing process（200-400℃）to obtain a porous V₂O₅nanorod film.The results show that the 3DOM structure experienced crystal core/amorphous shell structure to crystal nanorod phase transition during annealing,and that the aggregation and merger of V₂O₅nanocrystals,atomic rearrangement,and Ostwald maturation have important effects on nanorod formation.The diameter of the nanorods changes with the annealing temperature and time.In the 350℃-6 h V₂O₅porous nanorod film,the diameter of the nanorods is about 30-50 nm.The 350℃-6h V₂O₅nanopod porous film has excellent ion storage(98.77 mC cm^-2)and cycle stability（only 6.1%after 2000 cycles）,The transmittance modulation rangeΔT at wavelength 550 nm is 73.6%,and continuous pores between nanopod provide Li⁺a rapid diffusion channel with shorter response time（coloring 3.2 s,bleaching 3.9 s seconds）.Nanostructured V₂O₅films were prepared in situ on the ITO-coated glass substrate by the hydroheat-assisted solvent-gel method,and the V₂O₅film growth during hydroheat is influenced by the heterogeneous nucleation during hydroheat and the electrostatic attraction between the V₂O₅sols and the ITO substrate.During hydroheat,a small oxygen vacancy was introduced into the V₂O₅lattice and the concentration of oxygen vacancy was controlled by annealing treatment（temperature200 to 400℃at 4 h）.The 300℃V₂O₅film has the highest ion storage(112.25 mC cm^-2),transmittance modulation range of 65%at 550nm,5 and 5.2 s and 5.8 s respectively,and only 3.6%after 5000 cycles,excellent cycling performance attributed to the presence of gradient oxygen vacancies and good binding forces between the film and the ITO-coated glass.ECD was assembled with the 300℃-V₂O₅film prepared by the hydrothermal-assisted sol-gel method as ion storage layer,can change from light yellow to blue-black at different voltages,ΔT value of 87.8%at 550 nm,fast response time（bleaching/coloring:4.1/3.5 s）,CE value of 19.76 cm²C^-1,The ECD has excellent electrochromic properties.