Research On Preparation And Electrochromic Properties Of Nano-WO₃ Films And Amorphous LiMn₂O₄ Films

Electrochromic materials possess many advantages like lower electrochromic potential,variable changes in color,energy-saving,environmental friendly and so on.It is promising that they are widely used for smart windows,electronic papers,electrochromic displays,smart-wearable materials,etc.As for inorganic electrochromic materials,they do have many drawbacks like small optical modulation,slow switching speed,poor durability,single color change and low coloration efficiency.So WO3 and LiMn2O4 films are selected as the subjects of our experiments.The experiments are divided into two main parts.One is modifying the prqparation method to improve the electrochromic properties of WO3,and the other is exploring LiMn2O4 electrode as a new electrochromic material.The detailed results are listed as follows:(1)We employ single seed-layered spin-coating and hydrothermal method to prepare hexagonal WO3 nanowire films and then,we study the influences of ethylene glycol on the electrochromic properties of WO3 films.The experiment results show that once ethylene glycol was added,WO3 nanowire films would gain much larger optical modulation.When the wavelength was at 633nm,the transmittance change of WO3 nanowire film would be as large as 82.6%.Moreover,it can absorb most of the light at the range of 620?900 nm.Above all the listed merits,as-prepared WO3 films with the addition of ethylene glycol are favorable for their application in electrochromic smart windows.(2)We employ sol-gel method and dip-coating to prepare amorphous LiMn2O4 films and then,study the influence of additives like ethanol or 1,5-pentane-diol to the formation and electrochromic properties of LiMn2O4 films.The experiment results show that both of the additives are beneficial to the film formation.But only LiMn2O4 films using ethanol as additive possess outstanding electrochromic properties.Specifically,the transmittance change of LiMn2O4 films at 460nm was 43.4%,the switching speed was 2.6s for coloration and 1.9s for bleaching,and the coloration efficiency was 50.8 cm2·C-1.Moreover,it has multi-stage and multi-color electrochromic performance between colorless,greenish yellow and orange.And the apparent changes of absorbance are only in blue and purple regions,while keeping high transmittance in infrared region.So the LiMn2O4 films prepared by adding ethanol as the additive can be applied to information detection and electrochromic display fields and also meaningful to synthesis inorganic multicolor electrochromic materials.