Decoupling Stiffness and Toughness in Solid Polymer Electrolytes via Reversible Crystallization

Area of Science:

• Materials Science
• Polymer Chemistry
• Electrochemistry

Background:

• Solid polymer electrolytes (SPEs) offer flexibility and nonflammability for advanced electrochemical devices.
• Conventional SPEs face a trade-off: improving toughness often increases stiffness, leading to brittleness and poor electrode conformability.
• Thermally reversible crystals (TRCs) in polymers contribute to stiffness but limit stretchability.

Purpose of the Study:

• To decouple toughness from stiffness in solid polymer electrolytes.
• To create soft, tough, and stretchable SPEs using a novel material design strategy.
• To enhance the conformability and electrochemical performance of SPEs.

Main Methods:

• Utilized strain-induced crystallization (SIC) in a homogeneous four-branched poly(ethylene glycol) (Tetra-PEG) network.
• Introduced stiffness via TRCs of PEG to achieve both stiffness and fracture resistance.
• Investigated thermoplastic behavior upon heating for improved electrode conformability.

Main Results:

• Achieved significant toughness enhancement without increasing stiffness using SIC.
• Developed SPEs that are soft, tough, and highly stretchable.
• Demonstrated that reintroducing stiffness via TRCs results in stiff, fracture-resistant materials with thermoplastic properties.
• Achieved stable long-term cycling in Li|Tetra-PEG SPE|Li symmetric cells with reversible lithium plating/stripping.

Conclusions:

• The material design strategy effectively decouples toughness from stiffness in SPEs.
• Overcame conventional trade-offs in SPE development, enabling enhanced performance and safety.
• The developed SPEs show promise for next-generation stretchable electrochemical devices.