O3-type NaNi0.5Mn0.5O2 hollow microbars with exposed {0 1 0} facets as high performance cathode materials for sodium-ion batteries

O3-type layered transition metal oxides have been considered as the promising cathode candidates for sodium-ion batteries (SIBs) due to its high theoretical capacity. However, they generally suffer from critical issues like poor rate capability and inferior cycling stability. Herein, an O3-type NaNi0.5Mn0.5O2 hollow microbars with exposed {0 1 0} facets as well as uniform elements distribution has been synthesized via a facile ethanol-mediated co-precipitation method. The hollow architecture alleviates the volume strain during Na+ insertion/deinsertion and the exposed {0 1 0} facets enable a higher Na+ diffusion (about 4 times), which endow the electrode with a high reversible capacity of 133 mAh g−1, an outstanding rate capability (40 mAh g−1 at 30C) and remarkable long-cycle life (70.0% capacity retention over 500 cycles at 3.75C). Moreover, due to the suppression of the irreversible phase transition the midpoint voltage of the microbar electrodes is retained very well in compared to the large decay of the counterpart. This study may offer some insights into the structure design of high performance cathode materials for SIBs.