Hydrogen-bond-mediated interfacial chemistry enables reversible anodes for durable Sn-air batteries

Tin (Sn)-air batteries promise high capacity and environmentally benign chemistry, but their progress is fundamentally constrained by the poor reversibility of Sn anodes. The key intermediate Sn(OH)₃^- is electrostatically excluded from the Helmholtz layer, resulting in poor stripping/plating reversibility. Herein, we propose a urea-enabled interfacial regulation strategy to improve the reversibility of Sn anodes in which urea stabilizes the interfacial adsorption of the intermediate via hydrogen-bond binding to Sn(OH)₃^- and van der Waals coupling with carbon substrates. Molecular dynamics (MD) simulations revealed that the strong (urea)N-H···O(Sn(OH)₃^-) hydrogen bonding regulated the local solvation environment and reduced the desolvation free energy. In parallel, urea reorganized the electrical double layer (EDL) to form a more hydrophobic interfacial microenvironment, which suppressed hydrogen evolution. This achieved highly reversible Sn deposition/stripping, allowing symmetric cells to operate stably for >1000 h at 5 mA cm^-2 and full cells to deliver 381.2 mWh g^-1 with a cycling life of 769 h. This work establishes a hydrogen bond regulation strategy for Sn-air batteries to regulate the interfacial chemistry of anodes.