A Mesoporous Ferroelectric Separator for Inner Helmholtz Plane Homogenization Enabling Zinc Anode with High Reversibility

The aqueous zinc-ion batteries (AZIBs) are emerging as highly promising electrochemical energy storage solutions, owing to their advantages in safety and cost-effectiveness. However, the poor reversibility of zinc metal anode in aqueous electrolytes is the main bottleneck limiting their practical application. In this study, an easily fabricated mesoporous ferroelectric separator designed to significantly enhance the reversibility of zinc anode in aqueous electrolytes is introduced. The ferroelectric fields generated by this separator induce a uniform distribution of hydrated zinc ions between the inner Helmholtz plane (IHP) on the zinc surface and the bulk electrolyte, which in turn reduces the reactivity of parasitic reactions, such as hydrogen evolution and hydroxide formation. Meanwhile, the reduction of zinc reactivity, coupled with an increased zinc ion diffusion barrier, benefits planar zinc plating with minimal dendrite formation. Experimental evidence demonstrates that the zinc anode, equipped with the ferroelectric separator, achieves high reversibility in a standard 2 m ZnSO₄ aqueous electrolyte, with stable stripping/plating observed over 4000 cycles at various current densities. This study thus presents a novel separator for AZIBs that effectively mitigates parasitic reactions and dendrite growth by regulating the IHP structure, which offers a practical and low-cost pathway toward the actual application of AZIBs.