Although　the　rapid　development　of　electrical　energy　storage　devices　has　slowed　down　environmental　pollution,　their　large-scale　application　has　posed　huge　challenges　to　battery-related　mineral　resources;　thus,　extending　the　lifespan　of　high-voltage　lithium　cobalt　oxide　(LCO)　is　of　great　importance.　Surface　oxide　coating　is　considered　as　the　most　common　low-cost　modification　method　for　addressing　unstable　cycling　performance.　However,　studies　have　shown　that　the　oxide　layer　would　further　react　with　an　electrolyte,　while　the　investigation　on　the　corresponding　component　evolution　is　lacking.　Herein,　a　typical　example　utilizing　the　above　reaction　to　realize　surface　reconstruction　is　presented.　Applying　atomic　layer　deposition　(ALD),　originally,　an　ultrathin　Al2O3　layer　is　coated　on　the　LCO　surface;　however,　this　coating　layer　has　undergone　reconstruction　after　reacting　with　electrolyte　decomposition　products　during　the　cycling.　Compared　with　simple　coating,　the　in　situ　formed　Li3AlF6　layer　has　a　tighter　binding　to　the　LCO　surface　while　possessing　good　Li+　conductivity　and　electrochemical　stability.　In　addition,　the　unique　properties　of　the　ALD　technology　allow　us　to　achieve　ultrathin　(1　nm)　and　conformal　coating,　which　is　beneficial　for　electronic　conductivity　and　cycling　stability.　Furthermore,　the　surface　phase　transition　layer　stripping　failure　mechanism　has　first　been　revealed　to　explain　the　loss　of　Co　and　O,　while　the　reconstructed　Li3AlF6　effectively　suppresses　the　surface　stripping.　Thus,　excellent　high-voltage　performance　has　been　realized　(an　89%　capacity　retention　after　1000　cycles　at　4.5　V　and　an　88%　capacity　retention　after　200　cycles　at　4.6　V).　This　work　casts　a　new　understanding　on　the　surface　reconstruction　of　the　oxide　coating　layer,　which　is　also　significant　for　other　electrode　materials＇　modification.