Aqueous zinc metal batteries (AZMBs) are emerging as a promising alternative to lithium-ion batteries. However, challenges such as dendrite formation, hydrogen evolution reaction (HER), and ZnO passivation hinder their development. This study introduces a tetraalkylsulfonamide (TAS) additive to suppress HER, dendrite formation, and enhance cyclability. TAS displaces water molecules from the Zn²⁺ solvation shell, altering the solvation matrix and disrupting hydrogen bonds in free water. This is confirmed through ⁶⁷Zn and ¹H NMR, HRMS, and DFT studies. Voltammetry and in situ monitoring show suppressed dendritic growth and HER in the presence of TAS. Electrochemical mass spectrometry (ECMS) reveals TAS suppresses HER by an order of magnitude. TAS significantly improves cycle life, extending it from ~100 h to over 2500 h in coin cells. TAS also suppresses passivation product formation, enhancing Zn anode stability. The study demonstrates TAS's effectiveness in various electrolytes, including ZnSO₄ and Zn(OTf)₂, and its ability to stabilize Zn anodes regardless of counter-anion. TAS's low concentration (1 mm) and high stability-to-additive ratio make it a promising additive for high-performance AZMBs. TAS promotes uniform, non-dendritic Zn growth, reduces HER, and forms a conductive SEI layer. X-ray CT and FESEM analyses confirm TAS's role in preventing dendrite formation and ensuring uniform Zn deposition. TAS's ability to modulate solvation matrix energetics and suppress side reactions makes it a versatile additive for aqueous zinc metal batteries.Aqueous zinc metal batteries (AZMBs) are emerging as a promising alternative to lithium-ion batteries. However, challenges such as dendrite formation, hydrogen evolution reaction (HER), and ZnO passivation hinder their development. This study introduces a tetraalkylsulfonamide (TAS) additive to suppress HER, dendrite formation, and enhance cyclability. TAS displaces water molecules from the Zn²⁺ solvation shell, altering the solvation matrix and disrupting hydrogen bonds in free water. This is confirmed through ⁶⁷Zn and ¹H NMR, HRMS, and DFT studies. Voltammetry and in situ monitoring show suppressed dendritic growth and HER in the presence of TAS. Electrochemical mass spectrometry (ECMS) reveals TAS suppresses HER by an order of magnitude. TAS significantly improves cycle life, extending it from ~100 h to over 2500 h in coin cells. TAS also suppresses passivation product formation, enhancing Zn anode stability. The study demonstrates TAS's effectiveness in various electrolytes, including ZnSO₄ and Zn(OTf)₂, and its ability to stabilize Zn anodes regardless of counter-anion. TAS's low concentration (1 mm) and high stability-to-additive ratio make it a promising additive for high-performance AZMBs. TAS promotes uniform, non-dendritic Zn growth, reduces HER, and forms a conductive SEI layer. X-ray CT and FESEM analyses confirm TAS's role in preventing dendrite formation and ensuring uniform Zn deposition. TAS's ability to modulate solvation matrix energetics and suppress side reactions makes it a versatile additive for aqueous zinc metal batteries.