Aqueous zinc-ion devices are considered promising candidates for energy storage due to their high safety, low cost and relatively high energy density. However, the dendrite growth, hydrogen evolution reaction (HER) and corrosion of the zinc anode significantly limit the development of Zn-ion devices. Here, an inexpensive poly(3,4-ethylenedioxythiophene) (PEDOT) protective layer was constructed in situ on the Zn surface using electro-polymerization to suppress dendrite growth and side reactions, thereby enhancing the reversibility of Zn. Experimental and theoretical calculations revealed that this hydrophilic protective layer promotes the desolvation process of hydrated Zn²⁺ and facilitates the transport of zinc ions, thus improving the thermodynamic and kinetic properties of Zn²⁺ deposition and inhibiting interfacial side reactions. Consequently, the optimized PEDOT@Zn symmetric battery exhibited a cycling stability exceeding 1250 h at 0.5 mA·cm⁻² and 0.25 mAh·cm⁻², with a significantly reduced overpotential (from 91.8 to 35 mV). With the assistance of the PEDOT protective layer, the PEDOT@Zn//Cu battery maintained approximately 99.5% Coulombic efficiency after 450 cycles. Ex-situ scanning electron microscopy (SEM) and in situ optical microscopy characterizations further confirmed that the PEDOT protective layer can effectively suppress the growth of zinc dendrites. Additionally, the Zn-ion capacitors assembled by the PEDOT@Zn and activated carbon also demonstrated outstanding cycling stability.