Interfacial Charge-Transfer Kinetics Regulate Na₂S Deposition by Recycled V Single-Atom Catalysts for Durable Na-S...

Na₂S, as the terminal discharge product of room-temperature sodium-sulfur (Na-S) batteries, is electronically and ionically insulating. When it deposits as a compact film on the cathode, the cathode will become passivated, hindering electron transport and inhibiting further sulfur conversion reactions. Existing catalyst strategies promote the formation of Na₂S thermodynamically by enhancing polysulfide adsorption, but this does not address the kinetics passivation issue. Here, we adopt the exchange current density (j₀) as a kinetic descriptor of the Na₂S nucleation mode. Finite-element simulations reveal that increasing j₀ drives the nucleation pathway from progressive to instantaneous nucleation. The deposit morphology then evolves from a compact passivating film to uniformly dispersed nanoparticles, and ion and electron transport channels are preserved. This pathway prevents Na₂S aggregation and electrode passivation, maintaining electrochemical activity at deep discharge. Guided by this kinetic insight, nitrogen-doped porous carbon-supported V single-atom catalysts (NPC-V SACs) with high apparent j₀ were fabricated, and instantaneous Na₂S nucleation was achieved on their surfaces. The resulting Na-S battery retains 976.3 mAh g^-1 after 200 cycles at 0.2 A g^-1, with a decay rate of only 0.08% per cycle. This work establishes a kinetic design perspective for regulating Na₂S nucleation in durable Na-S batteries.