Preparation And Properties Of Tin Dioxide/Vanadium Pentoxide Composite Electrochromic Materials And Devices

Electrochromism is defined as the reversible changes in transmittance and reflectance of materials when different voltages are applied,which is caused by an oxidation–reduction reaction during an ion insertion or extraction process.Electrochromic materials are applied in many fields due to their special optical modulation,such as smart windows,color-changing glasses,energy efficient information displays,and military camouflage.Applying electrochromic materials to the field of camouflage is a giant challenge.Specifically,adaptive camouflage in the visible region requires materials to adjust their colors according to the color change of the background,to achieve the purpose of merging with the background,and realize perfect concealment from visual detection.In this thesis,vanadium pentoxide electrochromic materials are selected as the main research object.The multicolor electrochromic properties are similar to those of specific environments,and can be used as camouflage electrochromic materials.Composite electrochromic thin films with core/shell structure were prepared by hydrothermal and electrodeposition methods.Further,all-solid-state electrochromic devices were assembled by using the composite film,and the electrochemical and electrochromic properties of materials and devices were systematically studied.A core/shell structure of tin dioxide/vanadium pentoxide composite electrochromic film?SnO₂/V₂O₅?was prepared by hydrothermal and electrodeposition methods.In the composite material,the core is hydrothermally generated crystalline SnO₂ nanoflakes,and V₂O₅ is filled in the gap of the nanoflakes and coated on the nanoflakes by the electrodeposition method.The composite electrochromic film exhibits good electrochemical and electrochromic properties in the liquid electrolyte after heat treatment.Including stable electrochemical cycle stability,large transmittance modulation?47%at 450nm?,high coloration efficiency(118 cm² C^-1)and excellent optical cycle stability?still retained 85%of optical modulation after2000 cycles?.Importantly,the composite film achieves a highly reversible color change between yellow,green,and blue,indicating its potential application in adaptive camouflage in desert,oasis,and ocean conditions.An all-solid electrochromic device was prepared simply and efficiently using the above composite electrochromic thin film and polymer solid electrolyte.The UV-cured electrolyte has a strong bonding force to firmly bond the two electrodes of the device and test the device for a series of electrochromic properties.The bleaching and coloration times are 17s and 13s,respectively,and the coloring rate is 31.4 cm²C^-1,which still maintains 71.7%optical modulation after 100 cycles.The different color states of the device are also characterized by the Lab color mode,which shows a similar color change to the single electrode of the composite film in liquid electrolyte,and is expected to be applied in the field of military camouflage protection.The design and preparation strategy of all-solid-state electrochromic devices provides a new direction and important reference for the development of multicolor solid-state devices in the future.