Expanding　the　electrochemical　stability　window　(ESW)　of　aqueous　batteries　significantly　enhances　their　safety　and　energy　density,　addressing　performance　limitations　and　elevating　their　position　in　energy　storage　systems.　Over　the　past　decade,　water-in-salt　electrolyte　(WiSE)　has　led　to　groundbreaking　advancement　in　this　field.　However,　a　pressing　question　arises:　can　we　further　broaden　the　ESW　through　novel　approaches?　This　study　delves　into　this　question,　leveraging　atomistic　simulation　along　with　ESW　estimation　and　WiSE　continuum　theory　to　uncover　that　interfacial　solvent　polarity,　subtly　modulated　by　adding　minor　organic　solvents,　expands　the　ESW　as　well　as　promotes　ion　intercalation　and　transport.　The　strategy　of　incorporating　minor　organic　solvents　is　compatible　with　WiSE,　which　not　only　advances　our　comprehension　but　also　forges　new　research　paths　for　post-WiSE　era　aqueous　battery　innovation.　More　importantly,　our　study　provides　a　systematic　way　for　theoretically　estimating　ESW　and　analyzing　its　enhancement　mechanism　in　aqueous　batteries.　©　2025　American　Chemical　Society.