Owing　to　zinc　dendrites　and　parasitic　reactions,　aqueous　Zn-metal　batteries　often　suffer　from　poor　reversibility　and　cyclability.　Electrolyte　additives　present　a　promising　strategy　to　improve　Zn　anode　stability.　However,　the　ever-evolving　perspectives　and　mechanisms,　paradoxically,　complicate　battery　design,　causing　a　scenario　where　any　electrolyte　additive　seems　to　be　effective.　Herein,　it　is　taken　ionic　liquid　(IL)　additives　as　an　example　and　detailed　explored　the　impact　of　three　typical　IL　anions,　namely　OTF−,　TFA−,　and　BF4−.　It　is　identified　that　the　primary　determinant　of　electrolyte　additives　as　their　electrical　double　layer　(EDL)　structures　and　their　subsequent　solid-electrolyte　interface　(SEI)　composition.　An　advantageous　EDL　structure,　akin　to　an　ion-shield,　can　reduce　the　absorption　of　H2O　molecules,　which　further　enrich　the　SEI　with　zincophilic　and　hydrophobic　components,　thereby　mitigating　parasitic　reactions　and　Zn　dendrite　formation.　As　a　result,　the　Zn||Zn　cell　with　optimal　[EMIM]OTF　additives　demonstrates　an　exceptional　cycling　life　under　challenging　conditions,　its　cumulative　plated　capacity　surpasses　most　previously　reported　results　by　utilizing　different　IL　additives.　This　work　extends　beyond　performance　enhancements,　representing　a　valuable　exploration　of　key　criteria　for　electrolyte　additives　is　believed.　These　insights　are　expected　to　offer　fundamental　guidance　for　future　research　and　electrolyte　design.　©　2024　Wiley-VCH　GmbH.