Depressed P3-O3 phase transition in an O3-type layered cathode for advanced sodium-ion batteries

O3-type layered oxides are regarded as promising cathode materials for sodium-ion batteries (SIBs). However, they commonly exhibit complex phase transitions and sluggish Na+ kinetics, thus incurring poor capacity retention and rate capability. Here, O3-Na0.993Ni0.382Mn0.428Cu0.098Sn0.049O2 is obtained with Cu2+ and Sn4+ doped into the transition metal layers. It is found that the dopants Sn and Cu can enhance the electrostatic interactions between Na and O and improve the electrical conductivity, respectively. This reinforces its structure stability upon Na+ (de)intercalation and suppresses the Na+/vacancy rearrangement and the P3 -> O3 ' phase transition at high voltages. It exhibits a smooth charge/discharge curve, excellent cycling performance (80.7% capacity retention after 500 cycles) and good rate capability (108.5 mA h g-1 at 1000 mA g-1). This study provides new insights into designing novel layered oxide cathode materials for SIBs. The introduction of Cu2+ and Sn4+ ensures the remarkable structure stability of O3-Na0.993Ni0.382Mn0.428Cu0.098Sn0.049O2 to depress the Na+/vacancy rearrangement and P3 -> O3 ' phase transition, and hence good electrochemical performance.