Work-function-engineered high-entropy alloy/carbon nanofibers direct Na+ transport for stable anode-free sodium batteries
Anode-free sodium metal batteries (AF-SMBs) are promising for high-energy, low-cost energy storage, but suffer from interfacial instability due to sluggish Na+ kinetics and non-uniform deposition. Here, we report a scalable electrospinning-pyrolysis route to anchor FeCoNiCuMn high-entropy alloy (HEA) nanoparticles on N-doped carbon nanofibers (HEANCF). Density functional theory (DFT) calculations reveal high binding energy toward Na atoms, facilitating desolvation and adsorption. A built-in electric field (BIEF) arises from work function differences, driving electron redistribution and guiding uniform Na+ diffusion. The heterostructure also shows strong affinity for PF6− anions, promoting NaF-rich SEI formation that suppresses electron tunneling and parasitic reactions. Full cells with Na3V2(PO4)3 cathodes achieve 80% capacity retention after 600 cycles at 1 C. Ah-level pouch cells deliver ~200 Wh kg−1 and retain 87% capacity after 150 cycles at 0.5 C. This work establishes a coherent interfacial-kinetics framework for practical AF-SMBs.