Improvement of the sealing performance for sodium anode based battery by interface optimization of alpha-Al2O3/glass sealant

Highlight
• The interface between the glass and alpha-Al2O3 substrate was well optimized.
• The sealing performance of sodium battery was improved by surface modification.
• Various pre-treatments were applied to improve the Na-β″/β-Al2O3 film formation.
• The gradient film exhibited good chemical and thermal cycling stability.

A gradient film of Na-β″/β-Al2O3 was designed and fabricated by a gas–solid reaction method on the alpha-Al2O3 substrate surface to improve the sealing performance of alpha-Al2O3/glass interface. Scanning electron microscope (SEM), X-ray diffraction (XRD) and electron probe microanalysis (EPMA) were applied to characterize the film. The experimental results showed that pre-treatment of the alpha-Al2O3 substrate surface with MgCO3 or NaOH promoted the formation of Na-β″/β-Al2O3 film by generating intermediate phases of MgAl2O4 or sodium aluminum oxide. No obvious change was found from the film after 100 thermal cycles or heat treatment at 350 °C for 100 h, demonstrating its favorable thermal and chemical stability.