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

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 LiFePO₄ 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.