High-Strength, Thin, and Lightweight Solid Polymer Electrolyte for Superior All-Solid-State Sodium Metal Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Solid polymer electrolytes (SPEs) are crucial for all-solid-state sodium metal batteries due to flexibility and processability.
• Existing SPEs suffer from poor mechanical strength, excessive thickness, and instability with sodium anodes.
• Developing robust and thin SPEs is essential for advancing sodium battery technology.

Purpose of the Study:

• To fabricate a thin, mechanically robust, and cost-effective SPE for all-solid-state sodium metal batteries.
• To enhance the interfacial stability and overall performance of sodium metal anodes.
• To demonstrate the safety and cycling stability of batteries utilizing the novel SPE.

Main Methods:

• A polyethylene (PE) film was used as a skeleton for infiltrating poly(ethylene oxide)-sodium bis(trifluoromethanesulfonyl)imide (PEO/NaTFSI).
• The resulting PE-PEO/NaTFSI SPE was characterized for its thickness, mechanical strength, ionic conductivity, and interfacial properties.
• Na-Na symmetric cells and all-solid-state Na||PE-PEO/NaTFSI||Na3V2(PO4)3 coin cells were assembled and tested for cycling stability and critical current density.

Main Results:

• The novel SPE achieved a remarkable thickness of 25 μm with superior mechanical strength (100.3 MPa) and good flexibility.
• The electrolyte exhibited an ionic conductivity of 9.4 × 10^-5 S cm^-1 at 60 °C and enhanced interfacial stability with sodium metal.
• Na-Na symmetric cells demonstrated high critical current density (1 mA cm^-2) and long-term cycling stability (3000 h), while coin cells retained 93% capacity over 190 cycles.

Conclusions:

• The developed PE-PEO/NaTFSI SPE offers a promising solution for thin, high-strength, and safe solid-state electrolytes.
• This strategy effectively addresses the limitations of conventional SPEs in all-solid-state sodium metal batteries.
• The material's performance in pouch cells, including stability after abuse testing, highlights its potential for practical applications.