Direct　assembly　is　a　newly　developed　technique　in　which　a　cobaltite-based　perovskite　(CBP)　cathode　can　be　directly　applied　to　a　barrier-layer-free　Y2O3-ZrO2　(YSZ)　electrolyte　with　no　high-temperature　pre-sintering　steps.　Solid　oxide　fuel　cells　(SOFCs)　based　on　directly　assembled　CBPs　such　as　La0.6Sr0.4Co0.2Fe0.8O3−δ　show　high　performance　initially　but　degrade　rapidly　under　SOFC　operation　conditions　at　750　°C　owing　to　Sr　segregation　and　accumulation　at　the　electrode/electrolyte　interface.　Herein,　the　performance　and　interface　of　Sr-free　CBPs　such　as　LaCoO3−δ　(LC)　and　Sm0.95CoO3−δ　(SmC)　and　their　composite　cathodes　directly　assembled　on　YSZ　electrolyte　was　studied　systematically.　The　LC　electrode　underwent　performance　degradation,　most　likely　owing　to　cation　demixing　and　accumulation　of　La　on　the　YSZ　electrolyte　under　polarization　at　500　mA　cm−2　and　750　°C.　However,　the　performance　and　stability　of　LC　electrodes　could　be　substantially　enhanced　by　the　formation　of　LC-gadolinium-doped　ceria　(GDC)　composite　cathodes.　Replacement　of　La　by　Sm　increased　the　cell　stability,　and　doping　of　5　%　Pd　to　form　Sm0.95Co0.95Pd0.05O3−δ　(SmCPd)　significantly　improved　the　electrode　activity.　An　anode-supported　YSZ-electrolyte　cell　with　a　directly　assembled　SmCPd-GDC　composite　electrode　exhibited　a　peak　power　density　of　1.4　W　cm−2　at　750　°C,　and　an　excellent　stability　at　750　°C　for　over　240　h.　The　higher　stability　of　SmC　as　compared　to　that　of　LC　is　most　likely　a　result　of　the　lower　reactivity　of　SmC　with　YSZ.　This　study　demonstrates　the　new　opportunities　in　the　design　and　development　of　intermediate-temperature　SOFCs　based　on　the　directly　assembled　high-performance　and　durable　Sr-free　CBP　cathodes.　©　2017　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim