Metal-organic framework for dendrite-free anodes in aqueous rechargeable zinc batteries

Aqueous rechargeable zinc batteries (ZBs) have many advantages, such as eco-friendliness, low cost, and highrate performance. However, the Zn dendrite growth on the Zn metal anode of ZBs causes a short-circuit problem between the cathode and anode of the battery, resulting in the degradation of the cell performance. In this study, we employed a Zr-based metal-organic framework (Zr-MOF; UiO-66(Zr)-(COOH)2) with a poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) copolymer binder as a composite protective layer (CPL) to inhibit dendrite formation. The highly stable and porous metal-organic framework (MOF) in the CPL acted as a sieve allowing Znions to be uniformly deposited on the Zn anode. It effectively controlled the Zn dendrite formation during cycling. In addition, compared to a polyvinylidene fluoride (PVDF) homopolymer binder, the PVDF-HFP copolymer binder has a higher ionic conductivity and binding affinity with the Zr-MOF in the CPL, thus reducing the overpotential of the Zn symmetric cell and further improving its cyclability. As a result, the Zn symmetric cell, coated with the CPL composed of Zr-MOF and PVDF-HFP copolymer binder, exhibited stable operation for 2400 cycles at a high current density of 10 mA/cm2 without a short circuit. This result suggests that the combination of MOF materials and copolymer binders to design a CPL is efficient in suppressing Zn dendrites.

Automated summary

This study utilized a composite protective layer consisting of a Zr-based metal-organic framework and a polyvinylidene fluoride-hexafluoropropylene copolymer binder to inhibit dendrite formation on the zinc metal anode. The composite protective layer effectively controlled the deposition of zinc ions on the anode and improved the cycling performance of the battery.