Sodium-ion batteries have been achieving widespread attentions in grid-scale electrical energy storage systems owing to their earth abundant resources [1].However, the energy-density ceiling from cathode materials has been one of primary factors precluding the further practical applications of sodium-ion batteries [2].In comparison with various Na-based compounds such as tunnel/olivine/polyanionic-type oxides, transition metal (TM) layered oxides (NaxTMO2) have been regarded as one of the promising high-performance cathodes due to their high reversible capacity and tunable potentials [3].Differing from the layered electrodes of lithium-ion batteries, NaxTMO2 compositions can form P2 (ABBA), P3 (ABBCCA) and O3 (ABCABC) structures, as shown in Fig.1a, for which lithium strongly favors octahedral arrangements whereas sodium can adopt prismatic and octahedral coordination within layered structures [4].According to Delmas et al.[5], O and P refer to Na ions occupy octahedral and prismatic sites within alkali metal (AM) layer, respectively, in which the number represents the number of the periodically arranged oxygen stacking.These oxygen stacking sequences and Na sites directly influences on electrochemical performances.For instance, P2-type oxides usually provide higher Na+ conductivity and superior structural stability against the O3 analogues, corresponding to high power density and excellent long-term cycling performance.On the other hand, the reversible capacities in the first cycle are limited by the lower initial Na content of P2-type electrodes compared to high Na-content O3-type materials [6].However, there is still lacking of an effective guideline to the design and preparation of optimal Naion layered oxides.