The　particle　morphology　determined　by　the　sintering　process　is　the　director　factor　affecting　the　electrochemical　performance　of　Ni-rich　NMC　cathode　materials.　To　prepare　the　ideal　NMC　particles,　it　is　of　great　significance　to　understand　the　morphological　changes　during　sintering　process.　In　this　work,　the　morphology　evolution　of　LiNi0.8Mn0.1Co0.1O2　(NMC811)　synthesis　at　temperature　ranging　from　300-1080　degrees　C　were　observed　by　in　situ　SEM.　The　uniform　mixture　of　spherical　Ni0.8Mn0.1Co0.1(OH)(2)　precursor　and　lithium　sources　(LiOH)　was　employed　by　high　temperature　solid-state　process　inside　the　SEM,　which　enables　us　to　observe　morphology　changes　in　real　time.　The　results　show　that　synthetic　reaction　of　LiNi0.8Mn0.1Co0.1O2　usually　includes　three　processes:　the　raw　materials＇　dehydration,　oxidation,　and　combination,　accompanied　by　a　significant　reduction　in　particle　size,　which　is　important　reference　to　control　the　synthesis　temperature.　As　heating　temperature　rise,　the　morphology　of　mixture　also　changed　from　flake　to　brick-shaped.　However,　Ni　nanoparticle　formation　is　apparent　at　higher　temperature　similar　to　1000　degrees　C,　suggesting　a　structural　transformation　from　a　layered　to　a　rock-salt-like　structure.　Combining　the　insitu　observed　changes　in　size　and　morphology,　and　with　the　premise　of　ensuring　the　morphology　change　from　flakes　to　bricks,　reducing　the　sintering　temperature　as　much　as　possible　to　prevent　excessive　reduction　in　particle　size　and　layered　to　a　rock-salt　structure　transformation　is　recommended　for　prepare　ideal　NMC　particles.　(C)　2021　Science　Press　and　Dalian　Institute　of　Chemical　Physics,　Chinese　Academy　of　Sciences.　Published　by　ELSEVIER　B.V.　and　Science　Press.　All　rights　reserved.