Microstructural Densification of NASICON Solid Electrolytes Toward High-Performance Solid-State Sodium Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Ceramics Engineering

Background:

• NASICON-type oxide ceramics are promising sodium solid electrolytes but suffer from porosity and low density, hindering dendrite resistance.
• High-temperature sintering is typically needed for densification, but achieving theoretical densities remains difficult.

Purpose of the Study:

• To develop an efficient, low-temperature densification strategy for NASICON-type electrolytes.
• To improve the density and ionic conductivity of oxide electrolytes for solid-state batteries.

Main Methods:

• Utilized sodium tellurite (Na2TeO3, NTO) as a low-melting point (710°C) functional densifier.
• Employed liquid-phase sintering at lower temperatures enabled by NTO's early melting.
• Optimized NTO content (3 wt.%) for maximum density and performance.

Main Results:

• Achieved 97% relative density in NASICON ceramics using 3 wt.% NTO.
• Demonstrated a high room-temperature critical current density of 6 mA cm⁻².
• Symmetric cells showed stable sodium plating/stripping for over 1500 hours.
• Full cells with Na3V2(PO4)3 cathodes delivered 102 mAh g⁻¹ at 0.1C with excellent performance.

Conclusions:

• Low-melting point NTO enables efficient, low-temperature densification of NASICON electrolytes.
• This strategy significantly improves critical current density and cycling stability.
• The approach offers a scalable route to high-density, dendrite-resistant solid-state batteries.