Construction of Co/Ni-Free P2-layered metal oxide cathode with high reversible oxygen redox for sodium ion batteries

•A Co/Ni-free low-cost P2 layered sodium ions metal oxides cathode materials.•Highly reversibility and negligible phase transition with obvious anion reduction phenomenon.•XPS analysis proves that a large proportion of capacity above 4.3 V mainly originate form anion reduction.•DFT calculations suggest that the existence of weak Cu–O interaction stimulates oxygen-related activity.