Unlocking Solid-State Sodium-Metal Batteries at -15 °C by Electrolyte Optimization and Interface Regulation

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Beta-Al₂O₃ solid-state sodium metal batteries offer high energy density, safety, and low cost for large-scale energy storage.
• Challenges in room/low-temperature operation stem from low ionic conductivity and poor interfacial contact.

Purpose of the Study:

• To improve the low-temperature performance of Beta-Al₂O₃-based solid-state sodium metal batteries.
• To address challenges related to ionic conductivity and interfacial stability.

Main Methods:

• Incorporated Cu²⁺ into Beta-Al₂O₃ to enhance density and ionic conductivity.
• Introduced an In₂S₃ interface layer to form a mixed conductive layer (Na-In alloy and Na₂S) at the Na/Beta-Al₂O₃ interface.

Main Results:

• Symmetric batteries cycled over 2670 hours at room temperature (0.2 mA cm^-2) and over 3315 hours at -15 °C (0.025 mA cm^-2).
• The integrated strategy significantly improved interfacial electrochemical stability and Na⁺ transport.
• Full batteries demonstrated excellent cyclic stability and rate performance at both -15 °C and room temperature.

Conclusions:

• The developed strategy effectively overcomes low-temperature limitations in solid-state sodium metal batteries.
• This approach shows significant potential for practical applications in low-temperature energy storage systems.