Ion-Regulating SPEEK-BNNS Hybrid Interfaces Enabling Low-Barrier Zn-Ion Transport and Dendrite-Free Zinc Anodes

The practical application of aqueous Zn-ion batteries (AZIBs) is severely limited by unstable Zn-metal anodes caused by dendritic growth and parasitic interfacial reactions. Herein, we report an organic-inorganic hybrid protective layer composed of sulfonated poly(ether ether ketone) (SPEEK) and boron nitride nanosheets (BNNS), fabricated via a scalable and controllable spray-coating process. The hybrid architecture synergistically integrates the mechanical robustness of BNNS with the ion-regulating functionality of SPEEK, effectively addressing the trade-off between interfacial rigidity and ionic transport. This structure promotes uniform Zn²⁺ flux, suppresses dendrite growth, and stabilizes the Zn/electrolyte interface. Theoretical calculations, including density functional theory and nudged elastic band analysis, further reveal that SO₃H groups in SPEEK lower the Zn²⁺ adsorption energy and migration barriers, facilitating Zn²⁺ transport across the protective layer. The hybrid protective layer enables long-term stable Zn plating/stripping (>1800 h at 1 mA cm^-2, 1 mAh cm^-2) and uniform, dendrite-free deposition, as directly visualized by in situ optical microscopy. Consistent interfacial stabilization is further confirmed in Zn/MnO₂ full cells with improved rate capability and capacity retention. This work highlights a practical and rational interfacial design strategy for stabilizing Zn-metal anodes toward durable AZIBs.