POSS based ionic liquid as an electrolyte for hybrid electrochromic devices

The main objective of this study was to broaden the assortment of I−/I3− redox ionic liquids using polyhedral oligomeric silsesquioxanes (POSS) acting as nanobuilding blocks for the construction of functionalized 1,3-alkylimidazolium iodide solid (melting temperature 150–200 °C) and room temperature (RT) ionic liquids.The structural characteristics of the synthesised final ionic liquids and the corresponding intermediates were determined using 1H, 29Si NMR and infrared spectroscopic measurements. Raman spectra were next reported, in order to demonstrate the presence of polyiodides formed after the addition of iodine and the formation of redox electrolytes. Ionic conductivity values obtained from the impedance (EIS) spectra were determined in the temperature interval from room temperature up to 100 °C. Finally, a hybrid electrochromic cell was constructed from room temperature MePrIm+Ix− IO7 T8 POSS (x=1, 1.2, 3 and 5) ionic liquids encapsulated between a lithiated WO3 working and Pt counter-electrode, and colouring–bleaching changes assessed for cells cycled up to 1000 repetitive cycles.

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► Modification of alkyl imidazolium iodide IL by POSS leads to solid or viscous IL-s.
► Addition of iodine enhances conductivity to useful value.
► High viscous or solid electrolytes prevent leakage and enable easy production.
► POSS electrolyte is appropriate for roll-to-roll process for EC application.