Grain　boundary　engineering,　achieved　by　combining　annealing　and　surface　coating,　is　an　effective　strategy　for　modifying　high-nickel-layered　oxide　cathode　materials.　However,　high-temperature　annealing　can　induce　irreversible　phase　transformations　in　high-nickel　materials,　which　significantly　hinder　lithiation/delithiation　and　degrade　their　electrochemical　performance.　In　this　study,　we　propose　a　grain　boundary　engineering　approach　for　LiNi0.83Mn0.05Co0.12O2,　combining　rapid　heating　to　the　annealing　temperature　with　atomic　layer　deposition　(ALD)　to　enhance　its　electrochemical　properties.　Compared　to　conventional　heating,　the　rapid　heating　process　minimizes　Li/O　loss　and　prevents　the　formation　of　a　disordered　phase.　More　importantly,　grain　boundary　modification　and　bulk　gradient　doping　effectively　reduce　large　cracks　and　the　erosion　of　the　cathode,　which　slows　down　the　capacity　decay　during　long　cycles.　The　direct　heating　sample　exhibits　a　significant　improvement　in　capacity　retention,　and　after　stable　cycling　for　300　times　at　C/3,　the　capacity　retention　rate　remained　at　84.7%.　This　approach　offers　a　promising　low-cost　strategy　for　the　development　of　advanced　cathode　materials　with　enhanced　cycling　stability.　©　2025　American　Chemical　Society.