Aqueous dual ionic/electronic conducting binder enabling water-scarce, Zn2+-enriched interface for aqueous zinc metal batteries

Abstract

The development of aqueous zinc-ion batteries is crucial for advancing sustainable energy storage technologies. However, their widespread application is hindered by Zn corrosion and uncontrolled Zn dendrite growth. One promising approach involves creating a functional organic-inorganic interface on the Zn surface. Traditional binders, such as polyvinylidene fluoride (PVDF), fail to regulate water activity and ion migration, limiting the effectiveness of the interface. Herein, we introduce an aqueous dual ionic/electronic conducting binder, poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS), to build a water-scarce, Zn²⁺-enriched interface. Our findings demonstrate that PEDOT:PSS not only facilitates uniform distribution of inorganic fillers, forming a cohesive and compact interface, but also significantly enhances mechanical integrity. Additionally, the sulfonate groups within the binder matrix disrupt the hydrogen bond network of water molecules, reducing water activity and lowering the desolvation energy barrier of Zn(H₂O)₆²⁺ clusters. Therefore, the transference number of Zn²⁺ is elevated to 0.81 (compared to 0.61 with PVDF), mitigating undesirable side reactions and enabling dendrite-less Zn deposition. Consequently, symmetrical Zn||Zn cells with PEDOT:PSS binder demonstrate a lifetime with 4.2 times longer than those with PVDF. This work underscores the critical role of binder chemistry in stabilizing metal anodes for aqueous batteries.