Surface-Confined Lithium Plating Enabled by Externally Anchored MgF2 Nanodots on Hollow Carbon Spheres for Dendrite-free Anodes.

The advancement of lithium-metal anodes is critically hampered by uncontrollable lithium deposition, especially on lithiophobic three-dimensional carbon hosts where surface plating negates their structural benefits. While internal modification with lithiophilic agents (e.g., MgF2) is a common strategy, it often suffers from synthetic complexity and nanoparticle agglomeration, leading to inconsistent performance. Herein, we propose a strategic shift in host architecture by designing a composite where ultrafine MgF2 nanodots are uniformly anchored exclusively on the external surface of N-doped hollow carbon spheres (MgF2/NHCS). This precise external engineering, achieved via a controlled in situ conversion process, effectively prevents agglomeration and creates a continuous, homogeneous network of nucleation sites. This design enforces a conformal lithium-plating front, guiding the formation of a dense, spherical metallic layer that encapsulates the host. Concurrently, it synergistically fosters a highly robust, inorganic-rich solid-electrolyte interphase composed of LiF and Li3N. Consequently, the MgF2/NHCS host enables exceptionally stable, dendrite-free cycling over 1300 h in symmetric cells and delivers outstanding rate capability and longevity in full cells paired with LiFePO4. This work demonstrates the effectiveness of an external-modification paradigm, offering a scalable alternative to intricate internal designs for stabilizing lithium-metal batteries.