Physical rolling to construct sodium‑tin alloy interface to stabilize sodium metal anodes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium-metal batteries (SMBs) offer a low-cost, high-energy-density alternative to lithium-ion batteries.
• Key challenges include sodium dendrite growth and volume expansion, compromising battery lifespan and safety.
• Developing stable sodium anodes is crucial for practical SMB applications.

Purpose of the Study:

• To propose a facile physical rolling method for fabricating stable alloy anodes for SMBs.
• To investigate the formation and properties of a Na15Sn4 alloy layer on sodium metal.
• To evaluate the electrochemical performance and cycling stability of the modified sodium anodes.

Main Methods:

• Fabrication of Na15Sn4@Na alloy layer via repeated physical rolling of tin powder on sodium metal.
• In situ alloying to create abundant nucleation centers on the sodium anode surface.
• Density Functional Theory (DFT) calculations to analyze Na+ adsorption and surface energy.
• Electrochemical testing of symmetric and full SMB cells.

Main Results:

• The Na15Sn4@Na layer promotes uniform Na+ deposition and stripping, suppressing dendrite formation.
• DFT calculations confirm enhanced Na+ adsorption and diffusion kinetics.
• Symmetric cells demonstrated a cycling lifespan over 1070 hours.
• Full cells (Na15Sn4@Na||NVP) achieved 720 cycles at 2C with 80% capacity retention.

Conclusions:

• The simple physical rolling method effectively stabilizes sodium metal anodes.
• The Na15Sn4@Na alloy layer provides a scalable strategy for enhancing SMB performance.
• This approach offers a promising pathway for the development of safe and long-lasting SMBs for grid-scale energy storage.