Exploration And Development Of Hybrid Quasi-solid Polymer Electrolyte In Electrochromic Device

Electrochromism is a phenomenon with reversible change in light absorption,transmittance,and reflectivity of material caused by an applied voltage.With reversible transfer of electrons and ions,the material undergoes reaction with obvious color changes.This kind of material is an electrochromic material.Electrochromic material is used as working electrode and material with ion storage capability is used as counter electrode.Electrolyte is in the middle of the working electrode and counter electrode film.Two films are deposited on conductive glasses or other electrode materials and the device prepared in this sandwich structure is an electrochromic device(ECD).The electrochromic device has advantages of high optical modulation,low energy consumption and long memory effect etc.If light sensor is matched,ECD could intelligently control transmittance in the visible light to achieve goal of energy-saving and comfort.Electrochromic devices have now been commercialized in the fields of building exterior,smart windows and anti-glare rearview mirrors.However,most electrolytes used in electrochromic devices are still liquid electrolytes,which cannot be widely used in practice due to their risk of volatility and leakage.This dissertation proposes and discusses preparation and properties of a novel hybrid quasi-solid polymer electrolyte(QSPE).Viscous polyvinyl butyral(PVB)and modified polyethylene glycol(mPEG)were used to prepare QSPE.The effects of species and concentration of the materials on properties of electrochromic devices were also explored to optimize device performances.The details are as follows:First,polyethylene glycol was used to graft acrylate functional group at its terminal by polyaddition reaction,which was mixed uniformly with lithium perchlorate and photoinitiator to obtain modified polyethylene glycol(mPEG)prepolymer.Then,a porous PVB film was prepared by low boiling point solvent evaporation method.The as-prepared mPEG prepolymer was pumped into pores of PVB film under vacuum,and an electrochromic device(ECD)was prepared with electrochromic layer and ion storage layer.Experiments show that hybrid electrolyte prepared by this method has high adhesion,good luminous clarity(transmittance>70%in the visible region)and high ionic conductivity in the level of 10-2 mS cm-1.It was found that when the PVB content was 12 wt%,bonding stress of the hybrid QSPE had a 0.57 fold increase compared with mPEG electrolyte.Subsequently,an ECD was fabricated using poly 3,4-(2,2-dimethylpropylenedioxy)thiophene(PProDOT-Me2)and Li-Ti doped NiO as working and counter electrode respectively,and hybrid QSPE as electrolyte.Compared to ECD prepared with mPEG electrolyte,this electrochromic device can change from dark blue to colorless state with an optical modulation(△T)of 43.81%at 585 nm.Also it can maintain 84%of the initial △T value after 20,000 cycles,which provides guide for the study of solid polymer electrolytes.