Stabilizing Oxygen Framework in P3-Type Cathodes for Highly Reversible Sodium-Ion Batteries

P3-type layered oxides face challenges of voltage decay and capacity fading, which are primarily caused by the accumulation of oxygen vacancies (OVs) and irreversible oxygen loss during cycling. Herein, a cosubstitution strategy by incorporating Zn 2+ and Ti 4+ into the P3-Na 0.67 Ni 0.25 Mn 0.75 O 2 cathode material is proposed to synergistically stabilize the oxygen framework. The Zn 2+ dopant, with its stable d 10 electronic configuration and valence orbitals that occupy higher energy levels, suppresses anionic overoxidation, while the strong Ti–O bonding anchors the oxygen sublattice, collectively restraining the formation and diffusion of OVs. As a result of the improved oxygen stability, the generation of Mn 3+ and associated Jahn–Teller distortion is significantly reduced, as well. The modified cathode exhibits highly reversible structural evolution and remarkable cycling stability, retaining 90.0% of its capacity after 50 cycles. This work highlights OV management as an effective route to achieve stable P3 cathodes for sodium-ion batteries.