Highly Stable Zn Metal Anode Enabled By Atomic Layer Deposited Coating for Aqueous Zinc-Ion Batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted increasing attentions as energy storage technology for large-scale applications, because of low cost, inherent high safety and high capacity (820 mAh g-1 and 5854 Ah L-1). However, the poor rechargeability of Zn anodes limits their development, which is attributed to the dendrite growth, passivation and hydrogen evolution issues in the zinc anode. Herein, an untrathin coating enabled by atomic layer deposition was demonstrated for the protection of metallic Zn anode for aqueous ZIBs. By protecting Zn plate with the ultrathin layer, the Zn surface wettability was improved and the Zn corrosion was inhibited. As a result, the Zn dendrite formation has been effectively suppressed and lifetime has been significantly improved in Zn-Zn symmetric cells. More importantly, we have demonstrated the dendrites were mainly Zn(OH)2 species by the combination of characterization of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscope (HRTEM). With the optimized coating thickness, the surface-coated coated Zn symmetric cells have shown a reduced overpotential (36.5 mV) and a prolonged life span (over 500 h) at 1 mA cm-2. In addition, the surface-coated Zn has been verified in Zn-MnO2 batteries using layered δ-MnO2 as the cathodes and consequently superior electrochemical performance with a high capacity retention of 89.4% after over 1000 cycles at a current density of 1 mA cm-2 (3.33C for MnO2) is demonstrated. It is expected that the novel design of atomic layer deposition protected metal Zn anode will pave a new way to the realization of the high-performance aqueous Zn-ion batteries and as well shed light on the development of other metal anode-based battery systems.