Nitriles　as　efficient　electrolyte　additives　are　widely　used　in　high-voltage　lithium-ion　batteries.　However,　their　working　mechanisms　are　still　mysterious,　especially　in　practical　high-voltage　LiCoO2　pouch　lithium-ion　batteries.　Herein,　we　adopt　a　tridentate　ligand-containing　1,3,6-hexanetricarbonitrile　(HTCN)　as　an　effective　electrolyte　additive　to　shed　light　on　the　mechanism　of　stabilizing　high-voltage　LiCoO2　cathode　(4.5　V)　through　nitrites.　The　LiCoO2　lgraphite　pouch　cells　with　the　HTCN　additive　electrolyte　possess　superior　cycling　performance,　90%　retention　of　the　initial　capacity　after　800　cycles　at　25　degrees　C,　and　72%　retention　after　500　cycles　at　45　degrees　C,　which　is　feasible　for　practical　application.　Such　an　excellent　cycling　performance　can　be　attributed　to　the　stable　interface:　The　HTCN　molecules　with　strong　electron-donating　ability　participate　in　the　construction　of　cathode-electrolyte　interphase　(CEI)　through　coordinating　with　Co　ions,　which　suppresses　the　decomposition　of　electrolyte　and　improves　the　structural　stability　of　LiCoO2　during　cycling.　In　summary,　the　work　recognizes　a　coordinating-based　interphase-forming　mechanism　as　an　effective　strategy　to　optimize　the　performance　of　high　voltage　LiCoO2　cathode　with　appropriate　electrolyte　additives　for　practical　pouch　batteries.