Tailored Polymer‐Based SEI via iCVD for Stable Zinc Metal Anodes in Aqueous Batteries through Modulation of Hydrophilicity and Elasticity to Inhibit Hydrogen Evolution Reactions

Abstract Zinc is attractive for battery applications because of its high theoretical capacity, abundance, safety, low redox potential, cost, and toxicity. However, Zn suffers from poor reversibility due to its low coulombic efficiency, dendrite growth, and detrimental chemical side reactions, including the hydrogen evolution reaction (HER). A simple initiated chemical vapor deposition method for depositing 200‐nm‐thick superhydrophobic/elastic polymer coatings on Zn anodes as a protective artificial solid‐electrolyte interphase is demonstrated, which reduces the water activity to mitigate the HER and enhances the mechanical stability toward volume changes during cycling. Furthermore, density functional theory calculations show that the fluorinated polymer coating effectively reduces water activity, thus inhibiting the HER. A pouch‐type Zn||I 2 aqueous battery (5 × 5 cm 2 ) with a pF1V1 polymer coating delivered a capacity of 95 mAh at 4.6 mA∙cm −2 (≈1.2 C) and retained 98.4% of its capacity over 583 cycles. This study reveals novel prospects for incorporating superhydrophobic and elastic polymer compounds in Zn‐based battery research, offering a viable approach for enhancing cycling stability.