Abstract

P2-type Na_xNi_yMn_1–yO₂ cathodes have attracted attention due to their excellent stability and low cost, making them promising for sodium-ion batteries. However, their practical application is limited by a low capacity at lower voltages and severe phase transitions at higher voltage. To address these challenges, we report a material Na_0.6Ni_0.3Mn_0.7O₂–OVs (NNMO-OVs) with significantly slowed phase transitions at high voltage by introducing oxygen vacancies OVs into the P2/P3 mixed phase cathode Na_0.6Ni_0.3Mn_0.7O₂ (NNMO). Such a modification effectively broadens the Na⁺ diffusion pathways and enhances anionic redox reactions (ARR). As a result, an improved capacity of 173 mAh·g^–1 at 1C is obtained by the desirable cathode within a voltage range of 1.5–4.3 V. Even at 10C, it exhibits a capacity of 60.1 mAh·g^–1 between 2 and 4.1 V, maintaining 70.1% capacity retention after 700 cycles, showcasing impressive rate performance and cycling stability. Additionally, the P2/P3 mixed phase exhibits the presence of an OP4 intermediate phase during charging to high voltages, while the introduction of oxygen vacancies (OVs) further suppresses the P–O phase transition, maintaining only the P2-OP4 phase transition process.