Suppression of interfacial water layer with solid contact using an ultrathin, water-repellent, and Zn²⁺-selective layer for Ah-level zinc metal batteries

The failure of zinc metal batteries usually occurs due to the instability of the protection layer of the zinc metal anode caused by water penetration and metal dissolution during long-term operation, leading to an uncontrollably erratic electrode/electrolyte interface and the hydrogen evolution reaction. Herein, we propose an ultrathin, water-repellent, and Zn²⁺-selective layer to prevent the formation of the undesirable water layer and avoid water penetration. This interface, with an ultrathin thickness of 16.9 nm, was composed of a water-repellent didodecyldimethylammonium organic top layer and an open three-dimensional framework structure of inorganic layer with subnanometer pores and redox-active Fe centers that functioned as faradaic ion pumps, facilitating rapid Zn²⁺ transport. Consequently, the ultrathin solid contact layer acted as a semi-permeable membrane with a low water permeance of 0.000028 mol m⁻² h⁻¹ Pa⁻¹ while facilitating fast Zn²⁺ transport, thus suppressing the hydrogen evolution reaction. As a result, this layer enabled over 10 000 stable plating/stripping cycles at 5 mA cm⁻² with an average Coulombic efficiency of 99.91%. At a high rate of 150C, the Zn-I₂ cell operated for an unprecedented 65 000 cycles. Moreover, Ah-level Zn-I₂ pouch cells were fabricated, demonstrating scalable applicability towards grid-scale energy storage devices. Our work demonstrates the importance of designing stable and functional interface layers for metal anodes towards achieving high-energy metal batteries.