Poly(ionic liquid) Electrolytes for a Switchable Silver Mirror

Imidazolium-type small-molecule ionic liquids (ILs) and their corresponding poly(ionic liquid) (PIL) homopolymers were synthesized and applied to reversible electrochemical mirrors (REMs). The effects of alkyl chain length of the carbon chains at the N3 position and cation charge density (mono- and bis-imidazolium) on the electrochromic properties of Ag-based REMs were investigated by analyzing their electrodeposition and spectral properties. Longer alkyl chains and higher charge densities decreased the size and resulted in a more uniform distribution of Ag nanoparticles. Compared with IL-based liquid electrolytes, the PIL-based gel electrolytes formed smaller and denser electrodeposited metallic Ag nanoparticles because of their higher viscosity. These findings were used to guide fabrication of a 50 cm2 mirror dynamic window and flexible display. Because of several unique properties of PILs, the PIL-based REM exhibits fast switching speeds, superb cycling durability, small particle sizes, and uniform electrodeposited Ag nanoparticle films. These results make dynamic windows based on PIL electrolytes promising and competitive alternatives to traditional electrochromic windows.