Self-Evolving Gradient Alloy Layer Enables Stable Al Foil Anode for High Energy Lithium Batteries

Aluminum (Al) foil anodes, alloyed with lithium (Li), offer a theoretical capacity of 993 mAhg^-1 and are considered promising candidates for next-generation high-energy-density lithium-ion batteries (LIBs). However, their practical application is hindered by non-uniform alloying processes initiated by the native Al₂O₃ passivation layer, leading to severe structural degradation and electrode pulverization. Here, a self-evolving gradient alloy strategy is proposed that enables uniform Li alloying through the in situ construction of a lithiophilic zinc (Zn) interfacial layer on commercial Al foil via a scalable electroless plating process. The Zn interlayer initiates a low-barrier, sequential alloying pathway-from LiZn to LiAl-thereby promoting uniform lithium infusion, suppressing stress accumulation, and stabilizing the solid-electrolyte interphase (SEI). As a result, the Al@Zn anode achieves an ultralong cycling lifespan with a high Coulombic efficiency of 99.92% over 11 800 cycles, and powers full cells delivering an energy density of 452 Wh kg^-1. Comprehensive structural, electrochemical, and theoretical analyses confirm that the Zn-guided interfacial gradient effectively mitigates mechanical failure and interfacial instability. This work presents a practical and scalable interfacial engineering approach toward stable, high-performance alloy-type anodes, paving the way for the next generation of lithium-ion batteries.