Kosmotropic polymer crosslinking via boronic acid–diol chemistry enables conformal separators for high-rate aqueous zinc batteries

Aqueous zinc batteries (AZBs) have emerged as a compelling platform for energy storage owing to intrinsic safety, cost-effectiveness, and environmental compatibility. However, their practical implementation remains hindered by interfacial instability, dendritic zinc growth, and parasitic reactions associated with uncontrolled water activity. Separator modification offers a promising route, yet existing coating methods often suffer from limited chemical tunability and poor scalability for large-area fabrication. Herein, we introduce a separator engineering strategy based on boronic acid–diol crosslinking to form a thin and robust polymer network within porous substrates. This coating strategy enables conformal uniformity across porous structures while being compatible with scalable processing. Incorporation of zwitterionic MPC into the polymer design introduces kosmotropic groups that regulate interfacial water activity and suppress anion mobility. Consequently, the modified separator exhibits an enhanced Zn$^{2+}$ transference number (0.77), stabilized zinc deposition, and effective dendrite suppression. Zn||Cu asymmetric cells exhibit a high coulombic efficiency (99.9%) and long-term cycling stability under high-rate conditions (20 mA cm$^{−2}$). ... mehrThis work presents a chemically programmable and scalable coating strategy that unites crosslinking chemistry with kosmotropic regulation, establishing a generalizable materials design framework for stable aqueous zinc batteries.