Co-engineering dual Helmholtz planes and (101) facet-selective deposition for ultra-stable Zn metal anodes

The practical deployment of aqueous zinc metal batteries (AZMBs) is critically challenged by uncontrolled dendrite formation and parasitic side reactions, both arising from unstable interfacial chemistry. Herein, we propose a dual-region interfacial engineering strategy that concurrently regulates both the outer and inner Helmholtz planes (OHP/IHP) by introducing the N,N-dimethylethanolamine (DMEA) into the ZnSO4 electrolyte. In the OHP, DMEA coordinates with Zn2+ to reshape the solvation structure and attenuate Zn2+-H2O interactions, thereby lowering water activity and suppressing hydrogen evolution. Meanwhile, DMEA molecules chemisorb onto the Zn surface within the IHP, forming a robust organic interphase that homogenizes the electric field and promotes uniform Zn nucleation. This dual functionality guides crystallographic evolution toward the thermodynamically favorable (101) facet, which supports lateral Zn growth and effectively mitigates dendrite propagation. Benefiting from the interfacial-crystallographic synergy, Zn||Zn symmetric cells exhibit ultralong cycling stability over 5000 h at 1 mA cm−2 and maintain dendrite-free operation for over 1000 h at 5 mA cm−2. Furthermore, Zn||NH4V4O10 full cells deliver high specific capacities with 80.06 % capacity retention after 1000 cycles at 5 A g−1. This work offers a mechanistically guided and scalable electrolyte design that bridges solvation chemistry with crystallographic control, providing a promising route toward dendrite-free, high-efficiency AZMBs.