Ruddlesden Popper type oxide, La0.5Sr1.5MnO4+delta, is investigated as a potential electrode material for symmetrical solid oxide fuel cells. This work improves its electrochemical catalytic activity through over doping nickel to form a B-site excess oxide, (La0.5Sr1.5Mn)Ni0.1O4+delta. X-ray diffractometry shows that the over doped oxide has the Ruddlesden Popper structure when heated up to 800 degrees C in air and hydrogen atmospheres. Investigations with scanning electron microscopy, transmission electron microscopy and temperature-programmed reduction clearly demonstrate the exsolution of Ni nanoparticles from the parent Ruddlesden-Popper phase in hydrogen atmospheres. The Ni nanoparticles significantly improve the catalytic activity for hydrogen electro-oxidation reaction, reducing the interfacial polarization resistance at 800 degrees C by > 40%. Meanwhile, the B-site excess design improves the electro-catalytic activity for oxygen reduction reaction, reducing the interfacial polarization resistance at 800 degrees C by > 20%. As a result, the nickel enrichment design improves the peak power density at 800 degrees C by a factor of similar to 4 for the electrolyte supported model cells with symmetrical electrodes based on (La0.5Sr1.5Mn)Ni0.1O4+delta. The Ni enrichment design displays great prospects in improving the electrochemical performance for Ruddlesden-Popper type oxide as the electrode for symmetrical solid oxide fuel cells.