High-voltage water-scarce hydrogel electrolytes enable mechanically safe stretchable Li-ion batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Conventional soft Li-ion batteries using organic electrolytes suffer from moisture sensitivity, safety hazards from toxic fluorine compounds, and flammable solvent leakage.
• Mechanical damage to batteries can compromise their integrity and lead to performance degradation.

Purpose of the Study:

• To develop a mechanically robust and chemically safe stretchable Li-ion battery.
• To overcome the limitations of conventional electrolytes by designing a water-scarce hydrogel electrolyte with a fluorine-free lithium salt.

Main Methods:

• Design and synthesis of a water-scarce hydrogel electrolyte with a zwitterionic polymer backbone.
• Utilizing molecular dynamics simulations to understand the synergy between hydrophilicity and lithiophilicity.
• Fabrication and testing of soft Li-ion batteries under various mechanical stresses and ambient conditions.

Main Results:

• Achieved a wide electrochemical stability window (up to 3.11 V) and high ion conductivity (41 mS/cm).
• Demonstrated exceptional stretchability (1348%) and self-healing properties from cuts and punctures.
• Maintained stable operation for 1 month with over 500 charge-discharge cycles (95% average Coulombic efficiency) in ambient air without hermetic packaging.

Conclusions:

• The developed hydrogel electrolyte enables mechanically and chemically safe stretchable Li-ion batteries.
• The fluorine-free, water-scarce design offers a promising alternative for durable and reliable energy storage in flexible electronics.
• A prototype self-healing electronic system validated the practical application of these soft batteries as robust energy sources.