Electrochromic Device Composed of a Di-Urethanesil Electrolyte Incorporating Lithium Triflate and 1-Butyl-3-Methylimidazolium Chloride

A di-urethane cross-linked poly(oxyethylene)/silica hybrid matrix [di-urethanesil, d-Ut(600)], synthesized by the sol-gel process, was doped with lithium triflate (LiCF3SO3) and the 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) ionic liquid. The as-produced xerogel film is amorphous, transparent, flexible, homogeneous, hydrophilic, and has low nanoscale surface roughness. It exhibits an ionic conductivity of 3.64 × 10–6 and 5.00 × 10–4 S cm–1 at 21 and 100°C, respectively. This material was successfully tested as electrolyte in an electrochromic device (ECD) with the glass/ITO/a-WO3/d-Ut(600)10LiCF3SO3[Bmim]Cl/c-NiO/ITO/glass configuration, where a-WO3 and c-NiO stand for amorphous tungsten oxide and crystalline nickel oxide, respectively. The device demonstrated attractive electro-optical performance: fast response times (1–2 s for coloring and 50 s for bleaching), good optical memory [loss of transmittance (T) of only 41% after 3 months, at 555 nm], four mode modulation [bright mode (+3.0 V, T = 77% at 555 nm), semi-bright mode (−1.0 V, T = 60% at 555 nm), dark mode (−1.5 V, T = 38 % at 555 nm), and very dark mode (−2.0 V, T = 11% and −2.5 V, T = 7% at 555 nm)], excellent cycling stability denoting improvement with time, and high coloration efficiency [CEin = −6727 cm2 C–1 (32th cycle) and CEout = +2794 cm2 C–1 (480th cycle), at 555 nm].

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UID/QUI/00686/2016 UID/QUI/00686/2018 UID/QUI/00686/2019 PEst-OE/QUI/UI0616/2016 FCOMP-01-0124-FEDER037271 POCI01-0145-FEDER-016884 PTDC/CTM-NAN/0956/2014 SAICTPAC/0032/2015 POCI-01-0145FEDER-016422 POCI-010145-FEDER-030858 PTDC/BTM-MAT/30858/2017