Three-dimensional Zn foam coated with zeolitic imidazolate frameworks as stable zinc-ion battery anode

Abstract

Zinc-ion batteries (ZIBs) offer several advantages including low cost, safety, and high volumetric capacity. However, the potential of ZIBs is hindered by dendrite Zn growth, by-products, and hydrogen evolution resulting in poor lifespan. Herein, this study adopts three-dimensional Zn foams coated with zeolitic imidazolate framework (ZIF) as an anode for ZIBs for the first time. NaCl is selected as a spacer and mixed with Zn powder to vary the pore and strut size of Zn foams. The optimal condition for ZIF coating is investigated taking into account corrosion and electrical resistance as well as hydrogen evolution. The ZIF layer leads to the homogeneous Zn deposition and suppresses the hydrogen evolution and the by-product formation of zinc hydroxide sulfate. A Zn foam with a spacer size of >300 μm, which shows the most stable behavior during stripping/plating tests in a beaker cell, is also employed in symmetric coin-cell tests. Its excellent lifespan characteristic is demonstrated at 1 and 3 mA/cm2 for 1-h intervals over a duration of 300 h. Furthermore, ZIF-coated Zn foam and MnO2-filled Ti foam are assembled in full cells to evaluate the ZIB performance. The full cells show a capacity retention of 75.7 % over 100 cycles, demonstrating the potential of ZIF-coated Zn foam as a ZIB anode. This work provides a solution to practical anodes for ZIBs by maximizing the inherent structural advantages of Zn foam with the adequate coating of ZIF.