Enhanced Rate Capability and Cycle Performance of Titanium-Substituted P2-Type Na 0.67 Fe 0.5 Mn 0.5 O 2 as a Cathode for Sodium-Ion Batteries.

In this study, we developed a doping technology capable of improving the electrochemical performance, including the rate capability and cycling stability, of P2-type Na _0.67 Fe _0.5 Mn _0.5 O ₂ as a cathode material for sodium-ion batteries. Our approach involved using titanium as a doping element to partly substitute either Fe or Mn in Na _0.67 Fe _0.5 Mn _0.5 O ₂ . The Ti-substituted Na _0.67 Fe _0.5 Mn _0.5 O ₂ shows superior electrochemical properties compared to the pristine sample. We investigated the changes in the crystal structure, surface chemistry, and particle morphology caused by Ti doping and correlated these changes to the improved performance. The enhanced rate capability and cycling stability were attributed to the enlargement of the NaO ₂ slab in the crystal structure because of Ti doping. This promoted Na-ion diffusion and prevented the phase transition from the P2 to the OP4/″Z″ structure.
Competing Interests: The authors declare no competing financial interest.