A highly stable sodium solid-state electrolyte based on a dodeca/deca-borate equimolar mixture.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• All-solid-state sodium-ion batteries offer enhanced safety and energy density compared to traditional lithium-ion batteries.
• Developing stable and conductive solid electrolytes is crucial for realizing practical sodium-ion battery applications.
• Existing solid electrolytes often face challenges with conductivity, stability, or compatibility with sodium metal anodes.

Purpose of the Study:

• To introduce and characterize a new solid-state sodium electrolyte material.
• To evaluate the electrochemical and thermal properties of the novel electrolyte for battery applications.
• To assess the potential of this electrolyte for use in room-temperature all-solid-state sodium-ion batteries.

Main Methods:

• Synthesis of the novel sodium dodecaborate-dodecahydrododecaborate compound: Na₂(B₁₂H₁₂)_0.5(B₁₀H₁₀)_0.5.
• Measurement of Na⁺ ionic conductivity using electrochemical impedance spectroscopy.
• Assessment of thermal stability via thermogravimetric analysis.
• Determination of the electrochemical stability window through cyclic voltammetry.

Main Results:

• The synthesized Na₂(B₁₂H₁₂)_0.5(B₁₀H₁₀)_0.5 exhibits a high Na⁺ conductivity of 0.9 mS cm^-1 at 20 °C.
• The electrolyte demonstrates excellent thermal stability, remaining stable up to 300 °C.
• A large electrochemical stability window of 3 V was achieved, including stability against sodium metal anodes.

Conclusions:

• The new solid-state sodium electrolyte, Na₂(B₁₂H₁₂)_0.5(B₁₀H₁₀)_0.5, possesses key properties for battery applications.
• Its high ionic conductivity, thermal stability, and wide electrochemical window make it a strong candidate for solid-state sodium-ion batteries.
• This material is essential for the development of stable, room-temperature 3 V all-solid-state sodium-ion batteries.