New Insight into Ti Doping for Stabilizing the Na2/3fe1/3mn2/3o2 Cathode in Sodium Ion Battery

Iron- and manganese-based layered metal oxides, as cathodes in sodium ion batteries, have received widespread attention because of the low cost and high specific capacity. However, the Jahn-teller effect of Mn 3+ ions and resulting unstable structure usually leads to continuously capacity decay. Here, in this work, Titanium (Ti) has been successfully doped into Na 2/3 Fe 1/3 Mn 2/3 O 2 to suppress the Jahn-Teller distortion and improve overall performance of sodium ion batteries. In situ high-energy synchrotron X-ray diffraction (HEXRD) further shows that Ti-doped composites (Na 2/3 Fe 1/3 Mn 2/3-0.1 Ti 0.1 O 2 ) can maintain the single P2 phase without any phase transition during the whole charging/discharging process. In addition, various electrochemical characterization methods have been applied to confirm the improved transfer kinetics of Na + ions after Ti doping. In a word, this work provides a comprehensive insight into the Ti-doping effects on the performance from both structural and electrokinetic perspectives