P2-type layered oxide materials have attracted widespread attention as advanced cathodes for sodium-ion batteries due to their excellent rate potential and attractive cost-effectiveness. However, the unexpected dissolution of transition metal (TM) ions and the annoying Jahn-Teller effect leading to rapid capacity fading and low capacity remain obstacles to their commercial applications. To tackle these handicaps, we introduced a synergistic effect based on surface modification and doping strategies to obtain air-stable sodium carbonate (Na2CO3) protective aluminum (Al)-doped manganese-based layered oxide cathode. The surface Na2CO3 nanolayer is created by converting residual alkali ions, which enhances the air stability of the cathode and scavenges hydrofluoric acid into the fluoride-rich cathode electrolyte interphase layer during cycling, resulting in a steady interfacial interaction. In addition, Al doping causes TMO6-octahedral shrinkage and inhibits structural distortion, thereby affecting structural evolution and phase transition. These findings provide valuable insights into improving the performance of layer oxide cathodes for next-generation low-cost batteries.