Single-crystal layer-structured metal oxide cathode material for high-voltage sodium ion batteries

High-voltage cathodes offer increased energy density and rate capacity, which qualifies sodium ion batteries
(SIBs) for high-power applications. Since, transition metal oxide layered type cathodes are the most promising
candidates for sodium ion batteries. Recently, metal oxide layered single crystal materials have gained greater
attention as cathodes because of their high voltage capabilities. Herein, we report a single-crystal layer struc-
tured P2-typed Na0.66Ni0.33Mn0.67O2 (P2-NNM) oxide cathode material, synthesized via a high-temperature
solid-state method for high-voltage sodium-ion battery applications. Microscopic investigations clearly reveal
the single crystal morphology of the material, and X-ray diffraction pattern confirms the P2 phase with a high
degree of crystallinity. The observed lattice spacing of the single-crystal material is 0.562 nm. Electrochemical
studies of the cathode material unveil outstanding specific capacity of 170 and 218 mAh g-1 at 0.1C, when cycled
up to 4.5 and 5.0 V respectively. These results highlight the importance of developing of high- voltage single-
crystal layered cathode materials, and open a path way toward high-energy density sodium-ion battery
applications