Establishing Pinhole Deposition Mode of Zn via Scalable Monolayer Graphene Film

The uneven texture evolution of Zn during electrodeposition would adversely impact upon the lifespan of aqueous Zn metal batteries. To address this issue, tremendous endeavors are made to induce Zn(002) orientational deposition employing graphene and its derivatives. Nevertheless, the effect of prototype graphene film over Zn deposition behavior has garnered less attention. Here, it is attempted to solve such a puzzle via utilizing transferred high-quality graphene film with controllable layer numbers in a scalable manner on a Zn foil. The multilayer graphene fails to facilitate a Zn epitaxial deposition, whereas the monolayer film with slight breakages steers a unique pinhole deposition mode. In-depth electrochemical measurements and theoretical simulations discover that the transferred graphene film not only acts as an armor to inhibit side reactions but also serves as a buffer layer to homogenize initial Zn nucleation and decrease Zn migration barrier, accordingly enabling a smooth deposition layer with closely stacked polycrystalline domains. As a result, both assembled symmetric and full cells manage to deliver satisfactory electrochemical performances. This study proposes a concept of "pinhole deposition" to dictate Zn electrodeposition and broadens the horizons of graphene-modified Zn anodes.