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

Today Lithium (Li)-ion batteries are ubiquitous from portable electronics to electric vehicles and grid energy storage. However, Li-ion technology may not be sustainable in the long run; Li is scarce and comprises <0.0065% of the earth's crust. Aluminum (Al) on the other hand, is the most earth-abundant metal and offers an outstanding theoretical capacity due to three electron transfers per Al atom. However, traditional batteries that utilize Al-metal face a major obstacle: the formation of a passivating Al₂O₃ layer that blocks Al³⁺ movement. Here, an Al-based high entropy alloy (Al-HEA) is reported that enables efficient Al³⁺ transport while also stabilizing the Al-metal/aqueous-electrolyte interface. First-principles calculations reveal that the solid-solution structure of the Al-HEA leads Al atoms to transfer electrons to neighboring elements, which thermodynamically suppresses oxidation. Additionally, the Al-HEA's oxidation process is kinetically sluggish compared to pure Al, keeping the alloy/electrolyte interface open for Al³⁺ transport with minimal overpotential. Taking advantage of this, a high-performing aqueous Al-Selenium (Al-Se) battery is demonstrated that leverages this unique chemistry.