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.