A DPP2-HHTP-COF interfacial layer enabling ultra-long cycling stability of Sn anodes via electron-ion decoupling

Aqueous Sn-air batteries offer the advantages of low cost, high safety, and high theoretical capacity. However, Sn anodes are susceptible to the hydrogen evolution reaction (HER) and "dead Sn" detachment, leading to reversible capacity decay and severely limiting battery performance. Herein, we propose a DPP2-HHTP-COF mediated electron-ion decoupling strategy. An artificial electronically conductive DPP2-HHTP-COF interfacial layer is constructed on the Sn anode. The DPP2-HHTP-COF conjugated framework and electron-accepting units synergistically reconstruct the interfacial electronic structure, forming an electron-deficient layer and increasing the HER energy barrier. Meanwhile, the active coordination sites of the DPP2-HHTP-COF interfacial layer enable selective binding of SnO₂ ^2-, constructing dedicated ion-transport channels, optimizing Sn deposition/dissolution kinetics, and suppressing "dead Sn" formation. Consequently, interfacial stability is significantly enhanced. The assembled Sn-air battery with the DPP2-HHTP-COF@Sn anode achieves an ultra-long cycle life of 15 000 h (625 days) at 0.1 mA cm^-2, delivers 5291 stable cycles at 2 mA cm^-2/0.3 mAh cm^-2 with a coulombic efficiency approaching 100%, and maintains stable operation for ∼1150 h even at 60 °C. This work provides a molecular-level strategy for interfacial modification of Sn anodes and offers valuable insights for the development of high-performance aqueous Sn-based batteries.