Structural and surface-modified freestanding carbon nanofiber hosts for high-performance lithium-metal batteries

The commercialization of Li-metal batteries is limited by uncontrolled Li dendrite growth, causing short circuits and capacity degradation. Carbon nanofibers (CNFs) have been explored as 3D Li-metal hosts to reduce local current density, but their intrinsic lithiophobicity hinders uniform Li deposition. Herein, we report a freestanding 3D CNF scaffold decorated with ZnO and coated with SnO₂ via electrospinning and e-beam evaporation. The embedded ZnO particles serve as lithiophilic nucleation sites, guiding uniform Li plating throughout the structure. Meanwhile, the SnO₂ surface layer undergoes lithiation to form Li–Sn alloy and Li₂O, which enhance interfacial charge transfer and suppress dendrite formation. Notably, the SnO₂ coating induces a vertical electronic conductivity gradient across the scaffold, mitigating top-surface Li deposition and promoting stable, internal plating. Benefiting from this structural and gradient surface modification, the engineered electrode achieves a Coulombic efficiency of 97 % over 260 cycles at 1.0 mA cm⁻². At a high Li loading of 5.0 mAh cm⁻², the symmetric cell maintains a low overpotential (<30 mV) for over 900 h. A full cell coupled with LiFePO₄ delivers excellent cycling stability with 91.2 % capacity retention after 180 cycles at 1.0C. This strategy offers a promising route for safe, high-performance Li-metal batteries.