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

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 Na_0.67Al_0.02Fe_0.02Ni_0.02Cu_0.02Zn_0.02Mn_0.9O₂ 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.