Dense Lithium Deposition on Ultrathin Eutectic Sn–Bi–In Foils by Coupled Diffusion Doping and Dynamic Creep Wrinkling

ABSTRACT Ultrathin lithiophilic alloy foils (<10 µm) are highly desirable for advancing high‐energy‐density rechargeable lithium metal batteries toward practical applications, particularly in view of the persistent dendrite formation associated with pure Li anodes. Here, an ultrathin eutectic Sn–Bi–In alloy foil is fabricated through a simple melt–cooling–rolling process at 62°C. The foil enables uniform and dense Li deposition with an ultrahigh areal capacity of 200 mAh cm −2 through the synergistic effects of dynamic creep‐induced wrinkling, which guides Li nucleation, and elemental diffusion, primarily of In, which homogenizes the local Li + flux. The resulting dendrite‐free, columnar Li deposits exhibit excellent plating/stripping reversibility, sustaining stable cycling for 3500 h at 2 mA cm −2 and 1 mAh cm −2 with a low overpotential of only ∼13 mV. Full cells paired with LiFePO 4 cathodes achieve an average Coulombic efficiency of 98.69% over 600 cycles. These findings establish a scalable electrode design strategy that integrates mechanical adaptability with chemical self‐regulation, offering a promising pathway toward practical high‐energy‐density lithium metal batteries.