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 NaAlFeNiCuZnMnO cathodes with low-strain operation, which can significantly reduce the Mn 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.