Polymer Molecules Adsorption-Induced Zincophilic-Hydrophobic Protective Layer Enables Highly Stable Zn Metal Anodes.

Abstract

Zn metal, as one of the most promising anode materials for aqueous batteries, suffers from uncontrollable dendrite growth and water-induced parasitic reactions, which drastically compromise its cycle life and Coulombic efficiency (CE). Herein, a nonionic amphipathic additive Tween-20 (TW20) is proposed that bears both zincophilic and hydrophobic units. The zincophilic segment of TW20 preferentially adsorbs on the Zn anode, while the hydrophobic segment is exposed on the electrolyte side, forming an electrolyte-facing hydrophobic layer that shields the anode from active water molecules. Moreover, theoretical calculation and experimental results reveal that the TW20 additive can induce the preferential growth of (002) plane by adsorbing on other facets, enabling dendrite-free Zn anodes. Benefitting from these advantages, the stability and reversibility of Zn anodes are substantially improved, reflected by stable cycling for over 2500h at 1.0mA cm-2 /1.0 mAh cm-2 and 500h at 5mA cm-2 /5 mAh cm-2 as well as an average CE of 99.4% at 1.0mA cm-2 /1.0 mAh cm-2 . The full cells paired with MnO2 demonstrate a long lifespan for more than 700 cycles at 500mA g-1 . This work is expected to provide a new approach to modulate Zn electrode interface chemistry for highly stable Zn anodes.