Constructing Low‐Strain Cation Storage via High‐Entropy Doping to Stabilize Layered Oxide Cathodes for Advanced Sodium‐Ion Batteries

Abstract P2‐type manganese‐based layered cathode materials hold great promise for sodium‐ion battery applications. However, their practical implementation is hindered by structural instability caused by Jahn‐Teller distortion and complex phase transitions. Herein, this work proposes a simple and efficient high‐entropy doping strategy by introducing redox‐active and lattice‐stabilizing cations to elaborate sodium‐deficiency P2‐type Na0.67Al0.02Fe0.02Ni0.02Cu0.02Zn0.02Mn0.9O2 cathodes with low‐strain operation, which can significantly reduce the Mn3+ Jahn‐Teller active centers and enhance structural stability. In situ X‐ray diffraction results confirm that the high‐entropy doping strategy effectively mitigates volume strain of 1.58% during cycling with increased interplanar spacing and fast Na+ transfer kinetics, further maintaining a capacity retention of 88.81% with an average Coulombic efficiency of 99.90% after 600 cycles. This work provides valuable insights into the design of advanced sodium cathode materials for future low‐cost energy storage devices.