Dendrite-Free Anodes Enabled by a Composite of a ZnAl Alloy with a Copper Mesh for High-Performing Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (ZIBs) have attracted considerable attention because of their low cost, high intrinsic safety, and high volumetric capacity. However, unexpected dendrite growth and side reactions that arise at the Zn anode can severely hinder the mass adoption of ZIBs in practical applications. Herein, we report a dendrite-free ZIB anode via the hybridization of a eutectic ZnAl alloy with a copper mesh (denoted as ZnAl@Cu-mesh). The eutectic structure of the ZnAl alloy is composed of alternating Zn blocks and Al nanoflakes. The Al nanoflakes sacrificially consume the oxygen in the electrolyte to form an Al2O3/Al shell-core structure, which in turn guides the Zn deposition process by restraining the lateral diffusion of zinc ions and hence reducing the extent of dendrite formation. This process can synergistically reduce the likelihood of Zn passivation, which allows the Zn region to remain electrochemically active for the Zn stripping/plating process. Meanwhile, a copper mesh is used as a scaffold to provide uniform electric field distribution. As a result, the symmetric ZnAl@Cu-mesh//ZnAl@Cu-mesh cell presents appreciably low polarization (30 mV at 0.5 mA cm-2) and excellent cycling stability (240 h at 0.5 mA cm-2), as compared to Zn//Zn. Based on the postmortem investigation, ZnAl@Cu-mesh is able to retain a dendrite-free morphology after cycling at 1 mA cm-2, while significant dendrite formation can be observed for Zn. More impressively, the ZnAl@Cu-mesh//V2O5 full cell is able to achieve a 95% capacity retention after 2000 cycles at 2 A g-1, whereas its counterpart assembled with Zn fails after only 750 cycles because of short-circuit. Thus, the composite alloying strategy proposed in this work may provide an appealing direction toward the future development of dendrite-free anodes for rechargeable secondary batteries.