An approach to overcome first cycle irreversible capacity in P2-Na2/3[Fe1/2Mn1/2]O2

The Earth-abundant high capacity Na2/3[Fe1/2Mn1/2]O2 sodium-ion battery cathode material has been synthesized by conventional solid state synthesis. X-ray diffraction measurement shows the formation of the single phase Na2/3[Fe1/2Mn1/2]O2. Scanning electron microscopy shows particle size in the micron range having hexagonal morphology with high aspect ratio. To circumvent the first cycle irreversible capacity loss in Na2/3[Fe1/2Mn1/2]O2, NaN3 has been used as a source of extra Na ions added to the cathode mix. While pristine P2 type Na2/3[Fe1/2Mn1/2]O2 exhibits an irreversible capacity of 59 mAh/g, it reduces to 27 mAh/g after adding 5 wt.% NaN3 with concomitant nitrogen evolution in the half cell configuration. With further optimization, the combination of Na2/3[Fe1/2Mn1/2]O2 with NaN3 is promising for a viable sodium-ion cell.