Li-rich Mn-based layered oxide (LMLO) is a promising cathode for high energy density Li-ion batteries due to its high discharge capacity and low cost. However, the commercialization of LMLO is hampered by voltage fading, capacity decay and gas evolution during cycling due to interfacial side reactions. In this work, we designed a coating layer based on oxygen-deficient perovskite compounds La_0.9Sr_0.1CoO₃ (LSCO) using the Pechini that can capture the oxygen released during charging and suppress side reactions. Scanning transmission electron microscopy exhibit the coating layer is quite uniform with 6 nm thickness, and X-ray photoelectron spectroscopy demonstrate that the content of oxygen is significantly lower on the surface than that in the bulk material due to the oxygen vacancies within the LSCO coating layer. Compared with the pristine material, LSCO coated LMLO material exhibits higher initial coulombic efficiency, lower voltage decay, improved cycle and rate capability. In particular, the capacity retention at 2 C rate increases by over 50% after 400 cycles from 55.6% to 84.8%. Electrochemical impedance spectroscopy results demonstrate similar R_ct after activation of the two types of electrodes (coated and untreated), the charge transfer resistance increases rapidly upon cycling for the untreated LMLO electrodes, while there is essentially no change in R_ct for LSCO-coated LMLO electrodes. Postmortem analysis demonstrates that the LSCO layer inhibits electrolyte decomposition and excessive side reactions, forming a stable and Li+ conductive surface films on the LMLO cathode displays better electrochemical performance.