Polysiloxane-Based Single-Ion Conducting Polymer Electrolyte for Sodium Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Sodium-metal batteries offer higher energy density potential than sodium-ion batteries.
• The high reactivity of sodium metal poses a significant challenge for battery performance and safety.

Purpose of the Study:

• To develop a novel polysiloxane-based single-ion conducting polymer electrolyte (SIPE) for high-performance sodium-metal batteries.
• To address the challenge of sodium metal reactivity and enhance battery stability and energy density.

Main Methods:

• Synthesized a polysiloxane-based single-ion conducting polymer electrolyte (SIPE) by blending poly(vinylidene fluoride-co-hexafluoropropylene) and infiltrating with organic carbonates, creating NaPSiOM membranes.
• Evaluated ionic conductivity, electrochemical stability window, and cycling performance in symmetric Na║Na cells and full cells with Na3V2(PO4)3 (NVP) and Na4Fe3(PO4)2P2O7 cathodes.
• Tested performance under commercially relevant conditions, including high active material mass loading and large-area pouch cells.

Main Results:

• The NaPSiOM membranes exhibited high ionic conductivity (0.2 and 0.4 mS cm⁻¹ at 20 and 40°C) and a wide electrochemical stability window (>4.4 V).
• Achieved exceptional cycling stability in symmetric Na║Na cells (>2000 h) and long-term cycling in Na║NVP cells (>1000 cycles).
• Demonstrated stable cycling (>600 cycles) in room-temperature pouch cells with a Na4Fe3(PO4)2P2O7 cathode, even with high active material loading (18 mg cm⁻²).

Conclusions:

• The developed NaPSiOM exhibits excellent electrochemical properties and stability, making it a promising electrolyte for high-performance sodium-metal batteries.
• The electrolyte's performance is maintained under industrially relevant conditions, highlighting its practical potential.
• This work paves the way for the commercialization of safer and more efficient sodium-metal battery technologies.