NMC532　(LiNi0.5Mn0.3Co0.2O2)　is　a　cost-effective　and　structurally　stable　cathode　material　that　is　widely　used　in　batteries.　Despite　its　stability,　it　undergoes　irreversible　phase　transitions　and　transition　metal　(TM)　dissolution　during　long-term　cycling,　which　significantly　impacts　cell　performance.　This　study　pioneered　a　methodology　to　investigate　the　solid　electrolyte　interface　(SEI)　layers　in　depth,　employing　advanced　analytical　techniques:　time-of-flight　secondary　ion　mass　spectrometry　(TOF-SIMS)　and　cluster　analysis.　By　utilizing　these　techniques,　we　specifically　examined　the　impact　of　Mn　dissolution　on　the　interface　evolution　of　graphite　during　calendar　degradations.　Additionally,　we　explored　the　relationship　between　Mn　dissolution　and　cell　performance　in　a　graphite||NMC532　pouch　cell.　The　results　demonstrate　that　the　competition　between　Mn　dissolution　and　electrolyte　depletion　governs　cell　degradation.　In　particular,　Mn　dissolution　accelerates　the　decomposition　of　the　electrolyte,　ultimately　causing　SEI　layer　growth.　These　findings　provide　a　deeper　understanding　of　battery　performance　and　degradation　mechanisms.