<p>Aqueous zinc-ion batteries (ZIBs) are considered a promising candidate for replacing lithium-ion batteries in electrochemical energy storage applications. However, the commercial application of ZIBs is severely hindered due to dendritic growth, hydrogen evolution reaction (HER) of Zn anodes, leading to low Coulombic efficiency (CE), short cycle life, and reduced capacity. Herein, a cationic surfactant of polyquaternium-7 (PQ-7) is employed as a multifunctional electrolyte additive to address the issues. Combining experimental measurements and theoretical calculations, it can be found that PQ-7 is adsorbed at the initial tip position on Zn anodes to shield H₂O molecules, thus inhibiting HER. Such competitive adsorption behavior with Zn²⁺ could also mitigate the tip effect to promote uniform deposition instead of Zn dendrite during cycling. Due to the introduction of PQ-7, symmetric Zn∥Zn cells deliver ultrahigh cycling stability over 2117 h (5 mA cm⁻², 1 mAh cm⁻²). Meanwhile, the Zn∥Ti cell demonstrates a CE over 98% after 240 cycles. Furthermore, Zn∥MnO₂ batteries could afford a high-capacity retention of 92.1% after 1000 cycles at 1 C. Even at 5 C, the batteries could still retain 80% capacity after 1000 cycles.</p>