Cell‐Integrated In Situ Prelithiation Enables Stable and Fast‐Charging Self‐Supporting Al Foil Anodes

Self‐supporting aluminum (Al) foil anodes offer the advantages of high energy density, simplified structural configuration, and low cost. However, their practical application is severely constrained by challenges such as low initial Coulombic efficiency, pronounced interfacial side reactions, and sluggish lithiation kinetics. To address these bottlenecks, this study proposes an in situ prelithiation strategy implemented during the cell assembly stage. By bringing Al foil into direct contact with a thin lithium foil during cell fabrication, a spontaneous alloying reaction occurs during the resting period under electrolyte mediation, directly constructing an in situ prelithiated Al (IPL‐Al) foil anode within the sealed cell. It is demonstrated that this process simultaneously constructs a dual‐functional interphase structure consisting of a nanocrystalline/ultrafine‐grained LiAl host and a thin, inorganic‐rich solid electrolyte interphase (SEI). This structure lowers the nucleation barrier for subsequent lithiation, provides fast mass transport pathways, and helps suppress continuous side reactions while maintaining interfacial stability. Benefiting from this synergistic interfacial structural regulation, IPL‐Al exhibits significantly enhanced reaction kinetics and structural stability compared to pristine Al foil. The IPL‐Al||LiNi 0.8 Co 0.1 Mn 0.1 O 2 cell delivers a reversible discharge specific capacity of 211.1 mAh g −1 at 1C, with a capacity retention of 82.2% after 400 cycles. Even at a high rate of 5C, it maintains 80.3% of its capacity after 400 cycles. Furthermore, the IPL‐Al||LiFePO 4 cell exhibits only 11.2% capacity decay after 500 cycles. This work demonstrates that in situ prelithiation during the assembly stage is an effective strategy validated in full cells, providing new insights for the design and application of high‐performance, copper‐free, self‐supporting metal foil anodes.