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.