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 Zn²⁺ and Ti⁴⁺ into the P3-Na_0.67Ni_0.25Mn_0.75O₂ cathode material is proposed to synergistically stabilize the oxygen framework. The Zn²⁺ dopant, with its stable d¹⁰ 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 Mn³⁺ 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.