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P2‐type sodium‐manganese‐based layered cathodes, owing to their high capacity from both cationic and anionic redox, are a potential candidate for Na‐ion batteries (NIBs) to replace Li‐ion technology in certain applications. Still, the structure instability originating from irreversible oxygen redox at high voltage remains a challenge. Here, a high sustainability cobalt‐free P2‐Na_0.72Mn_0.75Li_0.24X_0.01O₂ (X = Ti/Si) cathode is developed. The outstanding capacity retention and voltage retention after 150 cycles are obtained in half‐cells. The finding shows that Ti localizes on the surface while Si diffuses to the bulk of the particles. Thus, Ti can act as a protective layer that alleviates side reactions in carbonate‐based electrolyte. Meanwhile, Si can regulate the local electronic structure and suppress oxygen redox activities. Notably, full‐cells with hard carbon (≈300–335 W h kg⁻¹ based on the cathode mass) deliver …