The　establishment　of　intimate　electrode/electrolyte　interface　is　very　important　in　solid　oxide　fuel　cells　(SOFCs),　because　it　plays　a　critical　role　in　the　overall　cell　performance　and　durability.　In　this　study,　Mn　segregation　and　interface　formation　between　directly　assembled　La0.8Sr0.2MnO3　(LSM)　electrode　and　yttrium-stabilized　zirconia　(YSZ)　or　gadolinium-doped　ceria　(GDC)　electrolytes　are　studied　using　combined　focused　ion　beam　and　scanning　transmission　electron　microscopy　(FIB-STEM).　In　the　case　of　LSM/YSZ　and　LSM/GDC　electrodes,　a　significant　reduction　in　the　electrode　ohmic　resistance　is　observed　after　cathodic　polarization　at　900　°C　and　500　mA　cm−2,　indicating　the　formation　of　an　intimate　interface.　However,　LSM　particles　start　to　disintegrate　at　the　electrode/electrolyte　interface　with　the　increase　of　polarization　time　in　the　case　of　LSM/YSZ　electrode.　On　the　other　hand,　the　LSM/GDC　interface　is　very　stable　with　negligible　microstructure　change　at　the　interface.　Mn　segregation　from　the　LSM　perovskite　structure　is　identified　under　the　influence　of　polarization　in　both　LSM/YSZ　and　LSM/GDC　electrodes.　The　results　demonstrate　that　nature　of　the　electrolyte　plays　a　critical　role　in　the　electrochemical　activity,　microstructure,　morphology　and　stability　of　LSM/electrolyte　interface　under　SOFC　operation　conditions.　©　2018