Modulation of the Fermi Level Pinning Effect Promotes Aluminum Deposition Kinetics for High‐Performance Aqueous Aluminum‐Ion Batteries

Rechargeable aqueous aluminum batteries (AABs) are considered one of the ideal candidates for large‐scale energy storage systems due to their high theoretical capacity and abundant elemental reserves. However, the passivating alumina layer and hydrogen evolution reaction (HER) at the aluminum (Al) metal anode seriously impede the application of AABs. Herein, we significantly reduced the high energy barrier of Al deposition on the alumina surface via a modulated Fermi‐level pinning (FLP) strategy, with drastically improved Al deposition kinetics and stable cycling performance in AABs. Benefiting from the mitigated FLP at the in situ constructed Sn/Al 2 O 3 interface configuration, the modified Al anode markedly enhanced the interfacial electron/ion kinetics and delivered one of the lowest initial Al deposition overpotentials of only 33 mV at 0.05 mA cm −2 , further verified by density functional theory (DFT) calculations. Moreover, by combining a hydrated eutectic medium to improve stability, the Al||Al symmetric cell with the optimized electrolyte exhibited superior cycling stability of over 880 h. Practically, the as‐prepared prototype pouch cells displayed high performance with above 161.4 mAh g −1 capacity after 450 cycles. Overall, the newly developed FLP strategy markedly enhances anode performance, and paves the new pathway towards AABs and other aqueous metal‐ion batteries.