A dual-site doping strategy to enhance the sodium storage performance of an O3-type layered sodium oxide cathode

The O3-type NaNi_1/3Fe_1/3Mn_1/3O₂ material is modified by introducing Sr²⁺ into the Na sites and Al³⁺ into the transition metal (TM) sites. The inactive Sr²⁺ and Al³⁺ serve as structural pillars within the NaO₂ and TMO₂ slabs, respectively, expanding the interlayer spacing and boosting the stability of the structure. The optimized cathode demonstrates a good rate performance of 117.8 mAh g^-1 at 5C and exhibits outstanding cycling stability of 88% after 200 cycles, significantly surpassing the pristine material (68%).