Physical and chemical properties of solvents and solutes are extremely important. For electrochromic applications,the electrolyte has sufficient amount of solute to ensure conductivity and mass-balance of ions between electrolyte and electrochromic materials. For instance ,an electrochromic device based on W03 and lithium electrolyte should have enough amount of Lit ion to achieve high modulation ratio of bleached to colored state, which requires about 20mC/ cm2.1 Furthermore,the ion-exchangeable hydroxyl sites in W03 consumes about 4x10-7M/cm2(i.e.,40mC/cm2) of Lit for W03 film with the density of 5.5g/cm3 and thickness of 0.55p m. Therefore the electrolyte should have at least 60mC/cm2(i.e.,6x 10 Mice) of Lit. If we use an electrolyte with 1M/9_ lithium salt, the necessary thickness of the electrolyte should be 6/Lm and finally the thickness of lithium-based electrolyte would be about 50- 60//m in order to avoid the change in conductivity before and after electrochromic reaction.
"Liquid electrolytes", Proc. SPIE 10304, Large-Area Chromogenics: Materials and Devices for Transmittance Control, 103040N (28 March 1990); doi: 10.1117/12.2283626; https://doi.org/10.1117/12.2283626