Unlocking high-rate O3 layered oxide cathode for Na-ion batteries via ion migration path modulation

O3-NaNi1/3Fe1/3Mn1/3O2is a promising layered cathode material with high specific capacity,low cost,and simple synthesis.However,sluggish kinetic hindrance is attributed to the size discrepancy between the large Na-ion and narrow tetrahedral interstitial positions,leading to inferior rate capacity and low reversible capacity.Herein,F with light-weight and strong electronegativity is introduced to substitute O atoms in the bulk structure,which intensifies the bond strength of transition metal and oxygen and enlarges the Na+diffusion channel.In addition,density-functional theory(DFT) calculations demonstrate that the electrostatic interaction is weakened between Na+in the tetrahedral site and the transitionmetal cation directly below it,dramatically reducing the migration barriers of Na+diffusion.Consequently,the as-obtained NaNi1/3Fe1/3Mn1/3O1.95F0.05sample displays outstanding rate performance of 86.7 mA h g^(-1)at 10 C and excellent capacity retention of 84.1% after 100 cycles at 2 C.Moreover,a full cell configuration using a hard carbon anode reaches the energy density of 307.7 Wh kg^(-1).This strategy paves the way for novel means of modulating the Na-ion migration path for high-rate O3-type layered cathode materials.