Slow　oxygen　reduction　reaction　(ORR)　is　a　key　obstacle　of　intermediate-temperature　solid　oxide　fuel　cells　(IT-SOFCs).　In　this　study,　we　prepared　a　complex　spinel　oxide　(Fe3+Co2+)(Fe2+Fe3+Co3+)2O4　as　good　ORR　catalyst　for　IT-SOFCs.　Inducing　oxidation　state　optimization　of　Fe　and　Co　ions,　the　strategy　of　Ni　doping　at　octahedral　sites　of　FeCo2O4　with　narrow　band　gap　can　effectively　facilitate　small　polaron　hopping　of　valence　electrons,　resulting　in　high　electrical　conductivity.　In　the　p-type　semiconductor　NixFe1-xCo2O4　(NFCOx),　the　strong　oxidant　Ni3+　and　highly　electronegative　Ni2+　would　capture　electrons　to　increase　hole　concentration　and　decrease　resistance.　The　substitution　of　Ni　that　is　smaller　in　size　for　Fe　of　bigger　size　at　B-sites　would　cause　lattice　distortion　and　structure　defects,　which　are　beneficial　to　the　promotion　of　oxygen　transport　capacity.　The　analysis　of　ORR　kinetics　based　on　the　distribution　of　relaxation　time　(DRT)　method　reveals　that　the　migration　of　adsorbed　oxygen　from　NFCOx　surface　to　the　triple-phase　boundary　(TPB)　is　the　rate-determining　step.　Owing　to　high　electronic　conductivity　and　fast　oxygen　transport,　power　density　as　high　as　1.93　W/cm2　at　800　°C　could　be　obtained　when　NFCO2-60GDC　composite　was　used　as　cathode　for　IT-SOFCs,　which　is　superior　to　(75.5%　higher)　that　of　using　commercial　LSM-based　cathode　(1.10　W/cm2　at　800　°C).　The　electrochemical　performance　of　NFCO2-based　IT-SOFCs　is　better　than　that　of　the　other　SOFCs　with　cathodes　reported.　©　2021