High-Entropy Solid-State Na-Ion Conductor for Stable Sodium-Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Solid-state sodium-metal batteries (SSBs) are promising for energy storage due to their safety and potential for high energy density.
• Developing high-performance solid electrolytes (SEs) remains a significant challenge for advancing SSB technology.

Purpose of the Study:

• To synthesize and characterize a novel high-entropy material as a solid electrolyte for SSBs.
• To evaluate the ionic conductivity, electrochemical stability, and performance of the developed SE in sodium battery systems.

Main Methods:

• Synthesis of high-entropy Na4.9Sm0.3Y0.2Gd0.2La0.1Al0.1Zr0.1Si4O12 via solid-state reaction at 950°C.
• Characterization of ionic conductivity, activation energy, and critical current density.
• Assembly and testing of sodium symmetric cells and solid-state Na3V2(PO4)3||SE||Na batteries.

Main Results:

• Achieved high room-temperature ionic conductivity of 6.7×10⁻⁴ S cm⁻¹ and low activation energy of 0.22 eV.
• Demonstrated excellent performance in Na symmetric cells, including high critical current density (0.6 mA cm⁻²) and stable cycling over 700 hours.
• Assembled solid-state batteries exhibited remarkable cycling stability with negligible capacity decay after 600 cycles and high Coulombic efficiency (>99.9%).

Conclusions:

• The synthesized high-entropy material shows significant potential as a solid electrolyte for high-performance SSBs.
• This work highlights the efficacy of high-entropy materials in designing advanced sodium-ion conductors.
• The findings offer a promising pathway for the development of safer and more efficient solid-state sodium-metal batteries.