Dual‐strategy modification on P2‐Na0.67Ni0.33Mn0.67O2 realizes stable high‐voltage cathode and high energy density full cell for sodium‐ion batteries

Abstract P2‐type Na 0.67 Ni 0.33 Mn 0.67 O 2 is considered as a potential cathode material for sodium‐ion batteries due to the merits of high voltage, low cost, and air stability. However, the unsatisfied cycling stability and rate performance caused by the destructive phase transition and side reactions hinder its practical application. Herein, we present a feasible dual strategy of Mg 2+ doping integrated with ZrO 2 surface modification for P2‐Na 0.67 Ni 0.33 Mn 0.67 O 2 , which can well address the issues of phase transition and side reactions benefitting from the enhanced structural and interfacial stabilities. Specifically, it exhibits a decent cycling stability with a capacity retention of 81.5% at 1 C and promising rate performance with a discharge capacity of 76.6 mA h g −1 at 5 C. The in situ X‐ray diffraction measurement confirms that the damaged P2–O2 phase transition is suppressed with better reversibility in high‐voltage region, whereas the side reactions are inhibited due to the protective ZrO 2 surface modification. Commendably, the full cell achieves an outstanding operating voltage of 3.57 V and a fabulous energy density of 238.91 W h kg −1 at 36.73 W kg −1 , demonstrating great practicability. This work is expected to provide a new insight for designing stable high‐voltage cathode materials and high energy density full cells for sodium ion batteries.