Regulating Lithium Plating Behavior in Lithium-Metal Batteries via Molten-Lithium Processing With Inorganic Additives

Lithium metal batteries (LMBs) are compelling candidates for next-generation energy storage owing to the ultrahigh theoretical capacity (3,860 mAh g^-1) and high energy density (400-500 Wh kg^-1). However, uncontrollable dendrite growth, severe volume change, low Coulombic efficiency, and the poor lithiophilicity of Cu current collectors have impeded practical deployment. Here, we report a self-assembled gradient interphase (SGI) produced in situ by reacting molten lithium with ZnF₂. The SGI exhibits a self-formed, vertically graded architecture. The SGI consists of a LiZn alloy sublayer that lowers nucleation overpotential and accelerates Li⁺ transport, and a LiF layer that offers high ionic conductivity and outstanding air stability for durable interfacial stability. The lower LiZn alloy layer promotes uniform lithium nucleation by providing a low diffusion barrier and strong interfacial affinity, while the upper LiF layer forms a stable, inorganic SEI that effectively suppresses dendrite growth. The symmetric cell equipped with the SGI Li-Zn-F interphase exhibited highly durable cycling, maintaining stable operation for 3000 h under 4 mA cm^-2/16 mAh cm^-2. This dual-layer configuration, in which distinct functional roles are spatially separated within the interphase, offers an advantage not attainable with conventional single-layer coatings.