Here, we report the design and fabrication of a cost-effective and high-performance composite (Bi_0.75Y_0.25)_0.93Ce_0.07O_1.5±δ–La_0.8Sr_0.2MnO₃ cathode by an in situ synthesis strategy with single-step phase formation and microstructure assembly, which shows lower cathode polarization resistance and better oxygen reduction reaction activity than the conventional LSM-based cathodes for low temperature solid oxide fuel cells.