A Stretchable and Safe Polymer Electrolyte with a Protecting-Layer Strategy for Solid-State Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Flexible batteries require safe, elastic electrolytes.
• Existing electrolytes often compromise safety or performance for flexibility.

Purpose of the Study:

• To develop a stretchable, nonflammable solid electrolyte for advanced flexible batteries.
• To enhance interfacial stability between the electrolyte and lithium anode.

Main Methods:

• Fabrication of a crosslinked poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) and triethyl phosphate (TEP) electrolyte.
• Incorporation of a poly(ethylene oxide) (PEO) protective layer for anode interface stabilization.
• Electrochemical testing of LiFePO4/Li cells and fabrication of a flexible battery prototype.

Main Results:

• Achieved ultrahigh elongation (450%), nonflammability, and ionic conductivity >1 mS cm⁻¹.
• Demonstrated a tougher, more stable solid-electrolyte interphase (SEI) with the PEO layer.
• LiFePO4/Li cells retained 85.0% capacity after 300 cycles; the flexible battery operated under various mechanical stresses.

Conclusions:

• The developed double-layer stretchable solid electrolyte offers a new paradigm for safe, high-performance flexible solid-state batteries.
• This approach addresses key challenges in electrolyte elasticity, safety, and interfacial stability.