Scalable Glass-Fiber-Polymer Composite Solid Electrolytes for Solid-State Sodium-Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Solid-state electrolytes are crucial for developing safer and more efficient sodium-ion batteries.
• Existing solid electrolytes often face challenges with mechanical stability, ionic conductivity, and interfacial compatibility with sodium metal anodes.
• Developing scalable and cost-effective manufacturing methods for solid electrolytes remains a key objective.

Purpose of the Study:

• To develop a mechanically robust, thin, and ionically conductive composite solid electrolyte (CSE) for sodium-ion batteries.
• To investigate the performance of CSEs fabricated using different sodium salts (NaClO4 and NaFSI) with sodium metal anodes.
• To demonstrate the potential of the optimized CSE in solid-state sodium-ion full cells.

Main Methods:

• Fabrication of CSEs by infiltrating polyethylene glycol diacrylate (PEGDA), polyethylene glycol (PEG), and sodium salts (NaClO4 or NaFSI) into a silica-based glass-fiber matrix.
• In situ UV-initiated polymerization to form the composite structure.
• Electrochemical characterization including symmetric cell testing for sodium stripping/plating and full cell performance evaluation.

Main Results:

• A thin (<50 μm), mechanically robust CSE was successfully produced using a scalable, ambient condition fabrication method compatible with roll-to-roll processing.
• The CSE incorporating NaFSI salt exhibited stable sodium metal stripping and plating at high current densities (0.67 mA cm⁻² at 60 °C), unlike NaClO4.
• Solid-state full cells utilizing the PEGDA + PEG + NaFSI CSE achieved full capacity utilization and demonstrated 70% capacity retention after 50 cycles at C/5 rate and 60 °C.

Conclusions:

• The developed glass-fiber-reinforced composite solid electrolyte offers a promising solution for mechanically stable and highly conductive separators in sodium-ion batteries.
• The use of NaFSI salt is critical for achieving stable cycling with sodium metal anodes.
• This fabrication strategy enables the development of high-performance, safe, and scalable solid-state sodium-ion batteries.