Biopolymer-based materials have been of particular interest and they are alternatives to synthetic polymers based on the decreasing oil resources. The polymer electrolytes were doped with choline-based IL N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide ([N-1 1 2(OH)[ENTf2]), or Er (CF3SO3)3 or both. The polymer electrolytes were employed in the production of glass/ITO/WO3/electrolyte/CeO2-TiO2/ITO/glass electrochromic devices (ECDs). The lowest onset temperature for the degradation of all the SPEs is at similar to 130 degrees C for the Gellan Er (CF3SO3)(3) (10:1) this temperature range of stability is wide enough for a material to be applied as an electrolyte/separator component in electrochemical devices. The three ECDs displayed fast switching speed (ca. 15 s). Gellan [N-1 1 1 2(OH)[NTf2] Er (CF3SO3)(3) (5:1:10) exhibited an electrochromic contrast of 4.2% in the visible region, the coloration efficiency attained at 555 nm was 3.5 and 0.90 cm(-2) C-1 in the "colored" and "bleached" states, respectively, and the open circuit memory was 48 h. Preliminary tests performed with a prototype electrochromic device (ECD) incorporating Wo(3) as cathodic electrochromic layer, are extremely encouraging. (C) 2015 Elsevier B.V. All rights reserved.