Organic Electronics for Electrochromic Materials and Devices. Hong Meng

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Figure 2.11 Schematic representation of the synthesis of PIL‐b‐CD and PIL‐Fc membranes and the hook‐and‐loop strategy for adhesion based on b‐CD and Fc‐modified PIL membrane surfaces.

      Source: Guo et al. [129].

      2.3.6 Gelatin‐Based Polymer Electrolytes

Natural polymers can become a promising substitute for synthetic polymers and cause great attention from researchers due to their biodegradability, eco‐friendliness, low production cost, and good physical and chemical properties. Among natural polymers, polysaccharides and proteins are best candidate due to their abundance in environment. Gelatin can be used as PE in EC applications. Gelatin is a polypeptide mainly composed of proline, hydroxyproline, and glycine. Avellaneda et al. [131] have reported a solid gelatin PE prepared by dissolving gelatin, LiClO₄, and glycerol into water for EC applications. The ionic conductivity for this electrolyte reached from 1.53 × 10⁻⁵ S/cm at room temperature to 4.95 × 10⁻⁴ S/cm at 80 °C. ECDs with the configuration K‐glass/Nb₂O₅:Mo EC‐layer/gelatin‐based electrolyte/(CeO₂)_x(TiO₂)_{1 − x} ion‐storage (IS) layer/K‐glass have been assembled and reported to increase the ionic conductivity and good long‐time cyclic stability [132]. Silva et al. explored a solid‐state ECD including gelatin‐based electrolytes [133]. This prototype ECD exhibited good optical density. The ECD display incorporating gelatine I and gelatine II samples presented in the visible region an average transmittance above 68% in the bleached state [133]. A novel gel electrolyte composition combining lithium iodide LiI in 1‐butyl‐3‐methylimidazolium iodide (BMII) IL, triiodide I₃⁻/I⁻ redox mediator, and biodegradable gelatin is proposed for ECDs (Figure 2.12) [134]. Fast switching times and high cycling stability, up to 20 000 cycles, are recorded in this ECD.

Figure 2.12 An ECD structure containing a gel electrolyte composition combining lithium iodide LiI in 1‐butyl‐3‐methylimidazolium iodide (BMII) ionic liquid, triiodide I₃⁻/I⁻ redox mediator, and biodegradable gelatin.

      Source: Reproduced with permission of Danine et al. [134].

Moreover, gelatin‐based electrolyte can be used in reflective ECD. Reflective ECD with glass/Cr/PB/electrolyte/CeO₂–TiO₂/ITO/glass configuration was reported to reveal a change from 8% to 15% at 450 nm for bleached and colored states.

Tihan et al. have used a new DNA–LiClO₄‐based solid PE in an ECD (Figure 2.13) [135]. The novelty of the present research consists in the use of DNA membrane with different LiClO₄ ratios in order to achieve new EC windows with good performances [135].

Figure 2.13 An electrochromic device containing DNA‐based electrolyte.

      Source: Tihan et al. [135].

2.4 Conclusion and Future Outlook

The field of PE is steadily broadening, as more and more various application are presented. Although lithium‐ion‐based electrolytes have been commercialized, such as applied in pull down window shades on Boeing 787 Dreamliner, smart glass in Ferrari 575 M Superamerica, and Flexity 2 light rail vehicles, some disadvantages such as poor safety, easy leakage, and unstable electrochemical performance limit its further development and wider applications. In this chapter, we have provided fundamental understanding of requirements for EC applications. In the meantime, recent progresses on polymer‐based electrolytes were summarized, including PEO/PVDF/PMMA gel polymer, self‐healing polymer, cross‐linking polymer, ceramic polymer, IL polymer, and gelatin PEs. The use of composite PEs has been identified as a promising method to improve the performance of electrolytes.

Table 2.1 Polymer hosts generally studied with the examples of gel polymer electrolyte complexes and their respective highest ionic conductivities.

Polymer electrolyte	EC materials	Ionic conductivity (S/cm)	Electrochemical stability window (V)	Optical modulation (%)	Stability	References
p(trimethylenecarbonate [TMC])/PEO	Prussian Blue/PEDOT	1.33 × 10−6	−1.5 ∼ 1	8 ∼ 30	Full color switch (>600 s)	[138]
PEO/PVDF	TiO2	6.98 × 10−6	—	СКАЧАТЬ В начало < 17 18 19 20 21 22 23 24 25 26 > В конец