Sodiophilic Hosts With Pseudocapacitive Kinetics for Robust Anode-Free Sodium Metal Batteries

Anode-free sodium metal batteries (AFSMBs) promise high energy density and simplified fabrication, yet require repeated sodium nucleation on the current collector surface after the complete stripping in each cycle. Here, we present a strategy utilizing sodiophilic hosts with pseudocapacitive kinetics to realize durable and efficient nucleation processes in AFSMBs, together with a scalable synthesis route for these hosts. To illustrate, a highly sodiophilic host was constructed by integrating pseudocapacitive T-Nb₂O₅ into amorphous carbon nanotubes (aCNTs) through in situ self-assembly. Experimental and theoretical results reveal that T-Nb₂O₅ domains can simultaneously preserve their structural integrity, minimize Na consumption, accelerate Na transport, and ensure reversible redox reactions, thereby establishing robust nucleation sites. Consequently, the T-Nb₂O₅@aCNTs host achieves highly reversible and uniform Na deposition, delivering an ultrahigh average Coulombic efficiency of 99.98% over 800 cycles in half-cells and long cycling over 900 h in symmetric cells under harsh conditions. When paired with a high-mass-loading Na₃V₂(PO₄)₃ cathode (15 or 30 mg cm^-2), the full cells exhibit high energy density and stable cycling performance. Moreover, the anode-free pouch cell maintains favorable capacity retention over 100 cycles at 2 C. The proposed host design concept with scalable manufacturing capability opens a universal pathway toward practical high-performance AFSMBs.