In this study, to avoid the surface segregation of La₂O₃ and LaNiO₃ phases on the lanthanum nickelate (La₂NiO_4+δ) infiltrated LSCF cathode, A-site deficient lanthanum nickelate (La_2-xNiO_4±δ) are investigated as the infiltrant. La_2-xNiO_4±δ (x=0-0.2) are synthesized and characterized first. The maximum deficient concentration of lanthanum is less than 0.2. La_2-xNiO_4±δ with higher deficient exhibits the enhanced electrical conductivity below 800^oC. Through the electrochemical impedance spectroscopy on the symmetrical cells, it is found that A-site deficiency lead to an increase in the polarization resistance. The surface charge transfer process gradually dominates the impedance with lanthanum deficiency increasing. In the infiltrated LSCF cathode, it is observed that about one order of magnitude decrease in polarization resistance has been achieved after La_2-xNiO_{4±δ ­}infiltration, with La_2-xNiO_4±δ)-infiltration being the smallest. In a short-term measurement, after 960 min cathodic polarization at -0.2V, the degradation of La_2-xNiO_4+δ (x=0-0.2) coated LSCF reduces with increasing A-site deficient concentration. The enhanced stability of La_2-xNiO_4+δ (x=0-0.2) coated LSCF demonstrates that A-site deficient La_2-xNiO_4+δ is one potential infiltration materials for LSCF cathode to improve the surface stability.