<p>Anode-free sodium metal batteries (AF-SMBs) have attracted considerable interest due to their high energy density and low cost, yet their practical deployment is hindered by interfacial instability stemming from sluggish Na⁺ kinetics and non-uniform deposition behavior. Here, we engineer FeCoNiCuMn high-entropy alloy (HEA) nanoparticles evenly anchored on N-doped carbon nanofibers (HEANCF) via a scalable electrospinning-pyrolysis route, achieving simultaneous modulation of Na deposition kinetics and interfacial Fermi-level. Density functional theory (DFT) calculations reveal that the HEANCF heterointerface exhibits high binding energy toward Na atoms, facilitating efficient desolvation and adsorption processes. Critically, a built-in electric field spontaneously formed at the interface due to the work function difference drives interfacial electron redistribution, guiding uniform Na⁺ diffusion and enhancing interfacial kinetics, thereby leading to homogeneous Na deposition. Moreover, the heterostructure demonstrates strong affinity for PF₆⁻ anions, promoting their preferential decomposition and forming a robust, NaF-rich solid electrolyte interphase, which effectively suppresses electron tunneling and parasitic reactions. As a result, the full cells employing Na₃V₂(PO₄)₃ cathodes demonstrate a capacity retention of 80% after 600 cycles at 1 C. Importantly, Ah-level pouch cells deliver ~200 Wh kg⁻¹ energy density and retain 87% capacity after 150 cycles at 0.5 C. This study pioneers a coherent interfacial-kinetics framework for practical, high-energy AFSMBs.</p>