Intermetallic Anodes Unlock Bulk Aluminum Incorporation in Aqueous Batteries

Aqueous aluminum-based batteries are attractive for safe and sustainable energy storage, but their development is limited by shallow Al utilization, surface passivation, hydrogen evolution, and sluggish anode kinetics. Here, we report an intermetallic-anode strategy that unlocks bulk Al incorporation through electrochemically driven Ni-Al alloying. Guided by alloying thermodynamics, Ni is identified as an effective Al host, and a high-surface-area Ni powder anode is constructed to make bulk alloying kinetically accessible beyond surface-limited deposition. The resulting Al-alloying Ni powder anode markedly reduces charge-transfer resistance and anode polarization, enabling stable symmetric-cell operation and long-duration full-cell cycling with a potassium nickel hexacyanoferrate cathode in a low-cost sulfate electrolyte, retaining 98.6% capacity after 6000 h at 0.1 mA cm^-2. When combined with electrolyte engineering, the full cell achieves 4000 cycles at 3 mA cm^-2 with 76.6% capacity retention, while a pouch cell with 4 cm × 5 cm electrodes maintains 72.6% retention after 150 cycles. Mechanistic analyses and density functional theory calculations reveal a Ni-assisted pathway that promotes uniform Al-containing deposition and improves the energetics of Al incorporation without intrinsically promoting hydrogen evolution. This work establishes intermetallic anodes as an active platform for bulk Al storage in practical aqueous batteries.