Insights into Ti Doping for Stabilizing the Na2/3Fe1/3Mn2/3O2 Cathode in Sodium Ion Battery

Iron-and manganese-based layered metal oxides,as cathodes for sodium ion batteries,have received widespread attention because of the low cost and high specific capacity.However,the Jahn-teller effect of Mn3+ions and the resulted unstable structure usually lead to continuously capacity decay.Herein,Titanium(Ti)has been successfully doped into Na2/3Fe1/3Mn2/3O2 to suppress the Jahn-Teller distortion and improve both cycling and rate performance of sodium ion batteries.In situ high-energy synchrotron X-ray diffraction study shows thatTi-doped compound(Na2/3Fe1/3Mn0.57Ti0.1O2)can maintain the single P2 phase without any phase transition during the whole charging/discharging process.Various electro-chemical characterizations are also applied to explore the better kinetics of sodium ions transfer in the Na2/3Fe1/3Mn0.57Ti0.1O2.This work provides a comprehensive insight into the Ti-doping effects on the per-formance from both structural and electrokinetic perspectives.