High-Entropy O3-Phase Cathodes with Enhanced Diffusion Kinetics and Lattice Stability for High-Power Na-Ion Batteries

O3-phase layered oxide cathodes have been considered as the most promising candidates for high-energy Na-ion batteries (SIBs) due to their high reversible specific capacity, yet the detrimental OP2 phase transition with severe c-axis contraction at high operating voltages hampers its power performance. Herein, we design and synthesize a novel high-entropy O3-phase cathodes, Na1.0(Ni0.4Fe0.2Mn0.4)0.83Zn0.06Cu0.01Ti0.08Ca0.02O2, with a configurational entropy of 1.53R. This high-entropy design significantly broadens the Na-ion diffusion channels and effectively mitigates c-axis contraction by stabilizing the lattice structure and suppressing phase transitions, thereby facilitating rapid Na-ion transport throughout the charge/discharge process. Consequently, the as-obtained cathode delivers a high specific capacity of 161.8 mAh g–1 at 0.1 C within 2.0–4.2 V and maintains a capacity of 122.1 mAh g–1 even at 5 C with a twofold improvement. In addition, 80.1% of initial capacity is retained after 100 cycles at 1 C, markedly higher than that of the counterpart (40.0%). These results highlight the critical role of high-entropy design in stabilizing the O3-phase cathodes for high-power SIBs.