A sodium-ion sulfide solid electrolyte with unprecedented conductivity at room temperature

Area of Science:

• Materials Science
• Electrochemistry
• Solid-state Chemistry

Background:

• Solid electrolytes are crucial for developing safer and more energy-dense solid-state rechargeable batteries.
• Current solid electrolytes face challenges in conductivity, stability, and processing temperatures.

Purpose of the Study:

• To report a novel sulfide sodium-ion conductor with high ionic conductivity.
• To investigate the effect of tungsten substitution on the properties of Na₃SbS₄.
• To demonstrate the potential of this material for advanced solid-state battery applications.

Main Methods:

• Synthesis of Na_2.88Sb_0.88W_0.12S₄ via partial substitution of Sb with W in Na₃SbS₄.
• Characterization of ionic conductivity using electrochemical impedance spectroscopy.
• Analysis of structural changes and phase transitions induced by tungsten doping.

Main Results:

• Achieved a record room-temperature conductivity of 32 mS cm^-1 in a sintered body of Na_2.88Sb_0.88W_0.12S₄, surpassing the benchmark Li₁₀GeP₂S₁₂.
• Tungsten substitution created sodium vacancies and induced a tetragonal to cubic phase transition, enhancing ion transport.
• The sulfide electrolyte demonstrated stability in humid atmospheres and required lower sintering temperatures compared to oxide conductors.

Conclusions:

• The developed Na_2.88Sb_0.88W_0.12S₄ is a highly promising fast sodium-ion conductor for solid-state batteries.
• This discovery facilitates the development of safer, cost-effective, and high-performance solid-state rechargeable batteries.
• The material's properties address key limitations of current battery technologies.