Ultra-trace polyvinyl alcohol induced interfacial solvation regulation for stable zinc metal anodes

Abstract

Aqueous zinc-ion batteries (AZIBs) are attractive for large-scale energy storage but remain limited by interfacial instability of zinc metal anodes (ZMAs), including dendritic growth, corrosion, and parasitic hydrogen evolution. Herein, we demonstrate an interfacial solvation engineering strategy enabled by an ultra-trace (ppb level) polymer additive that fundamentally alters zinc deposition kinetics without perturbing bulk electrolyte properties. Using polyvinyl alcohol (PVA)as an example, we show that the ultra-trace PVA introduced in zinc acetate electrolyte selectively participates in the Zn 2+ solvation structure at the electrode-electrolyte interface, forming interfacial [Zn(H2O)5(PVA)] 2+ complexes. This interfacespecific coordination lowers Zn 2+ desolvation barriers, homogenizes ion flux, and promotes preferential zinc growth along the thermodynamically favorable Zn (002) plane. As a result, zinc dendrite formation, corrosion, and hydrogen evolution are simultaneously suppressed. The Zn//Zn symmetric cells made with ppb-level PVA exhibit stable cycling for over 1700 hours, while the Zn//polyaniline full cells deliver long-term durability up to 1800 cycles with near-unity Coulombic efficiency. Importantly, the observed behavior is distinct from that induced by higher additive concentrations, revealing a non-linear, interface-dominated regime of electrolyte regulation. This work establishes ultra-trace interfacial solvation control as a powerful and cost-effective approach for stabilizing metal anodes in aqueous batteries.