Joule-Heated Ag Nanoparticle Functionalization of Lignin-Derived Carbon Fibers Enables Uniform Sodium Deposition

Sodium metal anodes promise high theoretical capacity (1166 mA h g −1 ) and a low redox potential, yet practical use is limited by poor coulombic efficiency and dendrite-induced safety risks. Herein, we engineer a silver-nanoparticle-decorated, lignin-derived carbon fiber host (Ag@LCF) via ultrafast Joule heating (≤1s, >1500 °C), which deepens graphitic ordering of the carbon matrix ( I G /I D = 0.815) and uniformly seeds sodiophilic Ag sites. The Ag nanoparticles play a dual role: they catalyze Na nucleation and furnish a percolated conductive network that lowers interfacial impedance. Density-functional theory reveals that Ag@LCF enables thermodynamically stable Na adsorption (down to –1.73 eV) with a minimized energy gap between dendritic and planar growth pathways (0.27 eV). This is attributed to Ag-C orbital hybridization, which modulates the local electronic environment, ensuring moderate charge transfer and stable bonding (ICOHP = 0.877 eV), thereby eliminating the electronic driving force for dendrite formation. This leads to dendrite-free sodium deposition, long cycling life (symmetric cell >250 h, full cell with 83.4% capacity retention over 300 cycles), and high-rate capability. By coupling ultrafast electronic-structure tuning of biomass-derived carbon with metal-nanoparticle interface engineering, this strategy advances safer, high-rate sodium metal anodes.