High Entropy Layered Cathode With Single Grain Morphology for High-Performance Sodium-Ion Batteries

A major obstacle in the advancement of sodium-ion batteries (SIBs) is the development of cathode active materials (CAMs) that offer both high specific capacity and long-term cycling stability. Among the various candidates, layered CAMs have attracted significant attention. In this work, we synthesized a high-entropy layered CAM with composition (Na_0.52Ti_0.19Mn_0.19Fe_0.21Ni_0.21Co_0.20O₂) using a spray pyrolysis technique, yielding large (0.75 µm on average) and separated grains. The resulting material comprises a P3-O3 layered oxide mixture, along with ∼20% rock-salt and spinel phases. This CAM demonstrates a high specific capacity (∼180 mAh g^-1 at 0.08 C), excellent rate capability (69% retention after 300 cycles at 1C), and high coulombic efficiency (>99.5%). In comparison, a CAM of identical composition synthesized via a conventional sol-gel method, exhibiting an agglomerated microstructure, showed lower capacity and retention, consistent with literature reports. These findings highlight the advantages of combining high entropy design and cathode morphology in developing next-generation cathodes for SIBs.