Gellan‐Gum and LiTFSI‐Based Solid Polymer Electrolytes for Electrochromic Devices

Abstract

It has been long recognized that solid polymer electrolytes (SPEs) are potentially interesting for solid‐state electrochemical devices. Gellan gum (Ge)‐based SPEs, plasticized with glycerol (Gly) and doped with lithium bis(trifluoromethanesulfone)imide (LiTFSI) were prepared by the solvent casting technique, and their properties were evaluated. LiTFSI‐based SPE systems exhibit, on the average, higher conductivities than similar systems with other lithium salts. The structure, morphology, complex impedance spectroscopy, cyclic voltammetry and thermal stability of the new electrolyte system were characterized. Electrochromic devices (ECDs) were built with optimized electrolyte samples and their performance was analyzed. The samples were applied in small ECDs with glass/ITO/CeO2‐TiO2/SPE/Prussian blue/ITO/glass configuration. The devices presented a two‐modulation operation: a semi‐bright mode (−2.5 V) and a dark mode (+0.5 V). The best results were obtained with the ECD containing the GeGly1Li2.4 electrolyte, for which the transmittance (T) values in the bleached and colored states were ca. 33.4/43.0 % and 5.4/8.8 % at 555/1000 nm, respectively. These results correspond to ΔT and ΔOD values of 28.0/34.2 % and 0.79/0.69, respectively, which give quite high CEin and CEout values of −4925 cm2 C−1 for bleaching (Qin=−272.1 μC cm−2), and 2062 cm2 C−1 for coloring (Qout=650.0 μC cm−2), at 630 nm. This electro‐optical performance suggests that the proposed SPE systems are promising materials to be further investigated and applied in ECDs.

Solid Polymer Electrolytes Based on Gellan Gum and Ionic Liquid for Sustainable Electrochromic Devices

“…The ionic conductivity obtained at 30 °C is high when compared to those obtained for gelatin and 1-ethyl-3-methylimidazolium acetate (1.2 × 10 –4 S cm –1 ), gellan gum with lithium iodide (LiI) (3.8 × 10 –4 S cm –1 ) and gellan gum lithium bis­(trifluoromethanesulfone)­imide (LiTFSI) (2.77 × 10 –4 S cm –1 ), applied in electrochromic devices. Regardless of the sample, it is detected that the ionic conductivity value increases as a function of temperature, as higher temperature increases the polymer chain segmental motion, leading to inter and intrachain ion movements that improve the ion hopping mechanism. , …”

Fundamentals and Advances of Electrochromic Systems: A Review

“…[106] However, ECDs which are used in displays are sometimes opaque (non-transparent) and transparency of the layers is not the main goal. [107] Considering an ECD, insertion, and extraction of protons (or any other small cation) and electrons in the EC layer, such as WO 3 , occurs under an electrochemical reaction. The conductivity of the layer can be changed during this ion insertion/extraction activity.…”

“…However, ECDs which are used in displays are sometimes opaque (non‐transparent) and transparency of the layers is not the main goal. [ 107 ]…”

Demonstration of a Gel-Polymer Electrolyte-Based Electrochromic Device Outperforming Its Solution-Type Counterpart in All Merits: Architectural Benefits of CeO2 Quantum Dot and Nanorods

“…15,16 polymer electrolyte (SPE) was utilized in the ECD configuration, and it has found growing research interest in the past decade. 17,18 However, the poor ionic conductivity and sluggish response time of SPEs led researchers to seek a modification in the existing SPE configuration, thus paving the path for a new class of electrolytes known as gel-polymer electrolytes (GPEs). The typical configuration of a GPE consists of a host polymer matrix accommodating a liquidphase electrolyte species.…”

“…Although electrochromic devices have been a research topic over the past five decades, their commercial applicability is still hindered by issues such as electrolyte leakage, electrolyte volatility, intricate edge-encapsulation process, and flammability in conventional liquid/solution-type ECDs. , To address such issues, a new class of electrolyte known as solid polymer electrolyte (SPE) was utilized in the ECD configuration, and it has found growing research interest in the past decade. , However, the poor ionic conductivity and sluggish response time of SPEs led researchers to seek a modification in the existing SPE configuration, thus paving the path for a new class of electrolytes known as gel-polymer electrolytes (GPEs). The typical configuration of a GPE consists of a host polymer matrix accommodating a liquid-phase electrolyte species .…”