Preparation And Properties Of All Solid Polymer/Lithium Perchlorate Electrolyte Membranes For Electrochromism

Electrochromic materials have reversible changes in optical properties driven by external voltage.Based on these optical characteristics,electrochromic materials and devices have been widely used in smart windows,goggles,anti glare rearview mirrors and other fields.With the development of the times and the progress of science and technology,the functionality of electrochromic technology has been continuously strengthened,and a series of new electrochromic materials and devices such as flexible,dual band and mid far infrared have emerged,expanding their applications in the fields of intelligent clothing,aerospace,multi-color display and so on.However,most of the existing studies use liquid or gel electrolytes to assemble electrochromic devices,resulting in narrow electrochemical window,high voltage,easy decomposition,difficult packaging,flammability and easy leakage.In contrast,all solid polymer electrolytes do not contain any organic solvents,have good mechanical properties,high electrochemical and thermal stability,simple preparation process and great development potential,but the low ionic conductivity of all solid electrolyte limits its rapid development.Therefore,it is an urgent problem to develop an all solid electrolyte with high permeability,flexibility and ionic conductivity and apply it to electrochromic devices.In view of the above problems,this paper plans to use lithium perchlorate(Li Cl O₄)as lithium source and polymer as frame material to obtain highly flexible all solid polymer electrolyte by using large-scale ball milling and hot pressing process and the addition of active filler:select a variety of different polymer matrices and make it clear that the optimal polymer matrix material is polyurethane(TPU)material;The effects of TPU with different molecular structures and lithium salts with different proportions on the ionic conductivity of electrolyte were investigated to determine the best formula;Through the addition of different organic/inorganic fillers,the ionic conductivity of electrolyte is further improved,and an all solid-state flexible electrochromic device is constructed.The effect of electrolyte conductivity on the cycle stability of the device is studied.The main research contents are as follows:Firstly,three kinds of solid-state electrolytes with different polymer matrices were prepared by ball milling and hot pressing using three polymers:polyethylene oxide(PEO),ethylene vinyl acetate copolymer(EVA),TPU and Li Cl O₄ as electrolytes.It was found that the ionic conductivity of TPU based polymer electrolyte was 8.7×10^-7 S/cm at room temperature,with excellent transmittance(?80%)and good mechanical properties,is an excellent choice for all solid polymer electrolyte.Secondly,the effects of different types of TPU and different contents of lithium salts on the ionic conductivity of electrolyte were further explored,and the polycarbonate TPU matrix and 15 wt.%Li Cl O₄ were determined as the best formula.The ionic conductivity of the prepared electrolyte membrane could reach 3.2×10^-6 S/cm at room temperature;Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate),PEDOT:PSS)film and polyaniline(PANI)film are used as cathode/anode color changing materials respectively to construct an all solid-state flexible electrochromic device.The device has obvious color changing effect,with optical contrast of 38.1%,coloring time and fading time of 13.0 s and 4.1 s respectively.After 2500 cycles,the optical contrast can be maintained at 30.8%.Finally,in order to further improve the ionic conductivity of polymer electrolyte,silicon dioxide(Si O2)and succinonitrile(SN)were used as fillers,combined with the regulation of proportion and composition,and the ionic conductivity of the prepared electrolyte membrane was1.3×10^-5 S/cm and 7.2×10^-6 S/cm,the ionic conductivity is significantly improved compared with that without filler.In addition,the printing layers of PEDOT:PSS electrochromic layer and the spraying layers of PANI electrochromic layer are changed to assemble all solid-state electrochromic devices respectively.It is found that the combination of printing three layers of PEDOT:PSS and spraying one layer of PANI layer is the best.Based on this,the electrochromic devices are assembled separately,and the response speed of the devices is improved,However,after 3000 cycles,the optical contrast is only18.8%,which may be related to the poor interface contact between electrolyte and electrochromic devices.The failure causes of electrochromic devices will be further studied in the future.