High‐Entropy Engineering of O3‐Type Layered Cathodes for Long‐Cycle Life Sodium‐Ion Batteries

Sodium‐ion batteries (SIBs) are increasingly regarded as promising alternatives to lithium‐ion batteries (LIBs) due to their abundant sodium resources, low cost, and similar electrochemical behavior. However, traditional cathode materials face issues such as poor cycling stability and low energy density, which severely limit the development prospects of SIBs. Herein, a high‐entropy engineering strategy is introduced to improve O3‐type binary transition metal oxides. Specifically, the NaNi 0.4 Mn 0.175 Fe 0.1 Ti 0.125 Sn 0.1 Li 0.05 Sb 0.05 O 2 material with precise Ti 4+ control demonstrates the best electrochemical performance. It delivers a discharge capacity of 73.4 mAh g −1 at a high current density of 20C (2.4 A g −1 ), and retains 83.3% of its capacity after 300 cycles at 1C. A series of electrochemical in/ex situ X‐ray diffraction and transmission electron microscopy characterizations demonstrate the effectiveness of the high‐entropy strategy in enhancing the structural stability of cathode materials. These results indicate that the stability of high‐entropy materials is determined by the synergistic effects of configurational entropy and element doping. Overall, this work provides valuable insights into the rational design of high‐performance cathode materials, offering a promising pathway for the advancement of SIBs technology.