Interfacial regulation and protection by conductive graphene coating induces highly reversible zinc behavior for durable aqueous zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) have the merits of high specific capacity, intrinsic safety, pro-environment, high abundance and facile battery assembly process. However, the metallic zinc anodes are troubled by uncontrolled growth of dendrite and unfavorable side reactions, resulting in inferior cycling durability and hindering its practical application. Herein, an effective strategy for regulating uniform electrochemical plating/stripping of zinc metal and alleviating side reactions via introducing a thin graphene coating on the metallic zinc substrate is provided. As expected, the achieved Zn@graphene electrode exhibited outstanding cyclic durability for over 4000 h with an extremely low voltage hysteresis (28 mV at 0.2 mA cm−2) and could withstand repeated plating/stripping process without significant voltage fluctuations for 480 cycles at ultra-high current density (10.0 mA cm−2). Furthermore, when switching between cycling and resting modes, the Zn@graphene electrode manifested highly reversible zinc behavior of 1500 cycles with remarkably stable voltage response, revealing the excellent anti-corrosion property and high reversibility. Comprehensive studies show that graphene coating could not terminate the dendrite formation and side reactions, but would guide uniform Zn-ion/electrolyte flux and homogenize electric field distribution to regulate the evenly electrochemical plating/stripping of zinc metal, and also serve as a protective barrier to reduce the risk of being pierced by the growing dendrite and randomly distributed by-products, thereby enhancing the electrochemical properties and improving the safety of aqueous ZIBs.