Stabilizing Lithium-Metal Host Anodes by Covalently Binding MgF₂ Nanodots to Honeycomb Carbon Nanofibers

Constructing lithiophilic carbon hosts has been regarded as an effective strategy for inhibiting Li dendrite formation and mitigating the volume expansion of Li metal anodes. However, the limitation of lithiophilic carbon hosts by conventional surface decoration methods over long-term cycling hinders their practical application. In this work, a robust host composed of ultrafine MgF2 nanodots covalently bonded to honeycomb carbon nanofibers (MgF2/HCNFs) is created through an in situ solid-state reaction. The composite exhibits ultralight weight, excellent lithiophilicity, and structural stability, contributing to a significantly enhanced energy efficiency and lifespan of the battery. Specifically, the strong covalent bond not only prevents MgF2 nanodots from migrating and aggregating but also enhances the binding energy between Mg and Li during the molten Li infusion process. This allows for the effective and stable regulation of repeated Li plating/stripping. As a result, the MgF2/HCNF-Li electrode delivers a high Coulombic efficiency of 97% after 200 cycles, cycling stably for more than 2000 h. Furthermore, the full cells with a LiFePO4 cathode achieve a capacity retention of 85% after 500 cycles at 0.5C. This work provides a strategy to guide dendrite-free Li deposition patterns toward the development of high-performance Li metal batteries.