How Does the Hydroxylated Carbon Chain Length in Polyol Electrolyte Additives Influence the Stability of Zn Anode?

Zinc (Zn) anode shows great potential for aqueous zinc-ion batteries yet faces persistent issues of dendritic growth and parasitic reactions at the interface. Here, six polyol additives with different hydroxylated carbon chain lengths are systematically studied under standardized conditions as interfacial regulators for optimizing Zn plating behavior. The calculations coupled with experimental analyses reveal a critical chain-length dependence: short-chain polyols prioritize Zn²⁺ migration and desolvation but insufficiently protect the interface, whereas long-chain polyols lead to excessive kinetic barriers despite effective interfacial stabilization. The polyol with an appropriate hydroxylated carbon chain length (erythritol) can balance thermodynamic stabilization with high Zn plating/stripping kinetics. The erythritol molecules spontaneously assemble into an adaptive monomolecular shield on the Zn anode, which simultaneously provides massive nucleation sites, modulates Zn²⁺ solvation structure, and establishes a robust hydrogen-bond network, resulting in dendrite-free Zn²⁺ deposition with minimal parasitic reactions. Remarkably, with a low concentration (10 mm) erythritol in the electrolyte, the Zn anode achieves excellent cycling stability for over 3400 h. This work not only presents a practical electrolyte additive, but also offers a critical principle for designing electrolyte additives for high-performance metal anodes.