High-capacity　electrodes　face　a　great　challenge　of　cycling　stability　due　to　particle　fragmentation　induced　conductive　network　failure　and　accompanied　by　sustained　electrolyte　decomposition　for　repeatedly　build　solid　electrolyte　interphase　(SEI).　Herein,　Se-solubility　induced　Sex2-　as　self-adjustment　electrolyte　additive　to　regulate　electric　double　layer　(EDL)　for　constructing　novel　triple-layer　SEI　(inner　layer:　Se;　mediate　layer:　inorganic;　outer　layer:　organic)　on　high-capacity　FeS2　anode　as　an　example　for　achieving　stable　and　fast　sodium　storage.　In　detail,　Sex2-　in　situ　generated　at　1.30　V　(vs.　Na+/Na)　and　was　preferentially　adsorbed　onto　EDL　of　anode,　then　converted　to　Se0　as　inner　layer　of　SEI.　In　addition,　the　Sex2-　causes　anion-enhanced　Na+　solvation　structure　could　produce　more　inorganic　(Se0,　NaF)　and　less　organic　SEI　components.　The　unique　triple-layer　SEI　with　layer-by-layer　dense　structure　alleviate　the　excessive　electrolyte　consumption　with　less　gas　evolution.　As　a　result,　the　anode　delivered　long-lifespan　at　10　A　g-1　(383.7　mAh　g-1,　6000　cycles,　93.1　%,　5　min/cycle).　The　Se-induced　triple-layer　SEI　could　be　also　be　formed　on　high-capacity　SnS2　anode.　This　work　provides　a　novel　SEI　model　by　anion-tailored　EDL　towards　stable　sodium-storage　of　high-capacity　anode　for　fast-charging.