Enhancing the Dendritic Tolerance of NASICON-Based Electrolytes by Grain Boundary Engineering

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• NASICON-type ceramics (Na_1+xZr₂Si_xP_3-xO₁₂) are promising solid-state electrolytes (SSEs) for all-solid-state batteries (ASSBs).
• Grain boundary properties significantly influence the performance and safety of SSEs.
• Developing SSEs with high ionic conductivity and mechanical stability is crucial for practical ASSBs.

Purpose of the Study:

• To propose and investigate a grain boundary modification strategy for NASICON-type ceramics using liquid-sintering.
• To enhance the performance of Na_3.3Mg_0.15Zr_1.85Si₂PO₁₂ (MNZSP) ceramics as SSEs.
• To improve dendrite inhibition and mechanical properties of SSEs for safer ASSBs.

Main Methods:

• Liquid-sintering method utilizing Na₃AlF₆ addition.
• Microstructural characterization of grain boundary phases.
• Electrochemical testing of symmetric and full cells, including critical current density (CCD) and cycling stability measurements.

Main Results:

• Addition of Na₃AlF₆ creates an amorphous and nanocrystalline grain boundary phase in MNZSP ceramics.
• This modification enhances mechanical strength and inhibits sodium dendrite penetration.
• Achieved high CCD of 2.1 mA cm^-2 and over 1200 h cycling stability in symmetric cells.
• Full cells demonstrated high capacity (99.1 mAh g^-1) and stable cycling for 200 cycles.

Conclusions:

• Grain boundary modification via liquid sintering is an effective strategy for developing high-performance SSEs.
• The enhanced MNZSP ceramics show great potential for practical, high-performance ASSBs.
• This approach offers a pathway to overcome key challenges in SSE development for safer batteries.