Suppression of Interfacial Water Layer with Solid Contact by an Ultrathin Water Repellent and Zn2+ Selective Layer for Ah-Level Zinc Metal Battery

Abstract

The failure of zinc metal batteries usually involves the instability of the protection layer of zinc metal anode due to the water penetrating and dissolution during long-term operation, leading to the uncontrollably erratic electrode/electrolyte interface and hydrogen evolution reaction. Here, we propose an ultrathin, water-repellent, Zn2+-selective layer to prevent the undesirable water layer and avoid the water penetrating and dissolution. This interface, with an ultrathin thickness of 16.9 nm, is 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 function as faradaic ion pumps, facilitating rapid Zn2+ transport. This ultrathin solid contact layer acts as semi-permeable membrane with low water permeance of 0.000028 mol m-2 h-1 Pa-1, while facilitating fast Zn2+ transport, thus suppressing hydrogen evolution. As a result, this layer enables 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 150 C, the Zn-I2 cell operates for an unprecedented 65,000 cycles. Moreover, Ah-level Zn-I2 pouch cells were verified, demonstrating scalable applicability towards grid-scale energy storage device. Our work demonstrates the importance of designing stable and functional interface layer for metal anode towards high-energy metal battery.