The application of deep eutectic solvents based on choline chloride or lithium chloride with ethylene glycol and glycerol as low-cost, recyclable and green electrolytes for electrochromic devices is reported.

The development of chloride free Deep Eutectic Solvents (DES) based on lithium acetate, triflate, bistriflimide, and sodium triflate combined with glycerol, ethylene glycol, and polyethylene glycol (PEG400) as suitable electrolytes was successfully applied in electrochromic devices (ECD). Reversible ECD incorporating selected DES as electrolyte and bipyridinium as electrochromic probes displayed a comparable performance to conventional systems, with slower transition times (2.5 times), improving the coloration contrast and efficiency (147.1 cm2. C−1 at 520 nm) and was stable for at least 1250 redox cycles.