An Oxidation-Resistant High Entropy Alloy for Aqueous Aluminum-Battery Chemistries

Aqueous Aluminum (Al)-metal batteries are impractical due to a passivating Al2O3 layer on Al-metal that impedes Al3+ diffusion. To overcome this challenge, an oxide interface that is thin enough to allow facile Al3+ transport, while also passivating the highly reactive Al-metal/water interface is needed. Here, we report an Al-based high entropy alloy that satisfies these conflicting requirements. First-principles calculations indicate that Al atoms in the solid-solution give up electrons to neighboring elements, thermodynamically suppressing the alloy’s tendency to oxidize. Besides this, we find that the alloy’s oxidation is kinetically sluggish compared to Al. Owing to these reasons, the alloy-water interface is permeable to Al3+ with a low overpotential that remains stable. Taking advantage of this, we demonstrate a high-performing aqueous Al – Selenium (Se) conversion chemistry battery.