Exploring a high capacity O3-type cathode for sodium-ion batteries and its structural evolution during an electrochemical process

An O3-layered oxide of NaFe0.25Mn0.25Ni0.25Ti0.25O2 was successfully synthesized. When serving as a cathode during sodium-ion cell operation, it exhibits excellent electrochemical performance. The operando XRD result reveals a reversible O3 → O3 + P3 → O1 + P3 phase transformation of NaFe0.25Mn0.25Ni0.25Ti0.25O2 during an electrochemical process.