La0.6Sr0.2Co0.2Fe0.8O3-delta　(LSCF)　is　the　most　intensively　investigated　high　performance　cathode　for　intermediate　temperature　solid　oxide　fuel　cells　(IT-SOFCs),　but　strontium　segregation　and　migration　at　the　electrode/electrolyte　interface　is　a　critical　issue　limiting　the　electrocatalytic　activity　and　stability　of　LSCF　based　cathodes.　Herein,　we　report　a　Nb　and　Pd　co-doped　LSCF　(La0.57Sr0.38Co0.19Fe0.665Nb0.095Pd0.05O3-delta,　LSCFNPd)　perovskite　as　stable　and　active　cathode　on　a　barrier-layer-free　anode-supported　yttria-stabilized　zirconia　(YSZ)　electrolyte　cell　using　direct　assembly　method　without　pre-sintering　at　high　temperatures.　The　cell　exhibits　a　peak　power　density　of　1.3　W　cm(-2)　at　750　degrees　C　and　excellent　stability　with　no　degradation　during　polarization　at　500　mA　cm-2　and　750　degrees　C　for　175　h.　Microscopic　and　spectroscopic　analysis　show　that　the　electrochemical　polarization　promotes　the　formation　of　electrode/electrolyte　interface　in　operando　and　exsolution　of　Pd/PdO　nanoparticles.　The　Nb　doping　in　the　B-site　of　LSCF　significantly　reduces　the　Sr　surface　segregation,　enhancing　the　stability　of　the　cathode,　while　the　exsoluted　PdJPdO　nanoparticles　increases　the　electrocatalytic　activity　for　the　oxygen　reduction　reaction.　The　present　study　opens　up　a　new　route　for　the　development　of　cobaltite-based　perovskite　cathodes　with　high　activity　and　stability　for　barrier-layer-free　YSZ　electrolyte　based　IT-SOFCs.