Designing Ionic Conductive Elastomers Using Hydrophobic Networks and Hydrophilic Salt Hydrates with Improved Stability in Air

• Published in: Advanced electronic materials Vol. 9; no. 6
• Main Authors: Yiming, Burebi, Zhang, Zhaoxin, Ali, Nasir, Lu, Yuchen, Qu, Shaoxing, Zhu, Shuze, Creton, Costantino, Jia, Zheng
• Format: Journal Article
• Language: English
• Published: Seoul John Wiley & Sons, Inc 01-06-2023; Wiley; Wiley-VCH
• Subjects: Condensed Matter; Conductors; Dehydration; Elastomers; Electrolytes; Fracture toughness; Hydrates; Hydrogels; hydrophilic; Hydrophilicity; hydrophobic; Hydrophobicity; Ion currents; ionic conductive elastomers; ionic conductors; Ionic liquids; Lithium; Mechanical properties; Moisture content; Physics; Polymers; Soft Condensed Matter; stability; Stretchability; Toxicity; Water
• ISSN: 2199-160X; 2199-160X
• DOI: 10.1002/aelm.202300069

Existing soft ionic conductors fall into two distinct categories: liquid‐rich ionic conductors containing large amounts of liquid electrolytes (≈70–90 wt.% water for hydrogels and ≈20–80 wt.% ionic liquids for ionogels), and liquid‐free ionic conductors that do not contain liquid components (e.g., ionic conductive elastomers). However, they are often plagued by dehydration, leakage of toxic ionic liquids, and air aging. Here, using hydrophobic polymer networks and hydrophilic salt hydrates, ionic conductive elastomers (s‐ICEs for short) containing only a tiny amount of bound water (≈1–5 wt.% are synthesized). Thanks to the small embedded water content, the s‐ICEs are advantageous over liquid‐rich ionic conductors in terms of enhanced mechanical/electrical stabilities and safety; they also outperform previously reported liquid‐free ionic conductors by avoiding air‐aging issues. The s‐ICEs introduced here also show excellent stretchability, good elasticity, high fracture resistance, desirable optical transparency and ionic conductivity, which are comparable to those of state‐of‐the‐art liquid‐rich and liquid‐free ionic conductors. With all the above advantages, the s‐ICE represents an ideal material for practical applications of soft ionotronics in ambient conditions.
Liquid‐based or liquid‐free ionic conductors are often plagued by dehydration, leakage of toxic ionic liquids, and moisture‐induced property changes. This work introduces a novel ionic conductor system by hydrophobic/hydrophilic integrated design. Thanks to the small amount of bound water (≈1–5 wt.%), the stability of the mechanical and electrical properties of the material are improved significantly.