Synergistic Modulation of Localized Chemistry and Cationic Potential in High‐Entropy Biphasic Cathodes for Advanced Sodium‐Ion Batteries

Abstract The O3‐NaNi 0.5 Mn 0.5 O 2 is considered a promising cathode, while its capacity degradation resulting from structural damage and the inherent Na + diffusion barrier have posed significant challenges in practicability. Herein, a dual modification strategy is proposed by constructing a biphasic high‐entropy cathode material, i.e. Na 0.796 Ni 0.3 Mn 0.47 Al 0.03 Zn 0.03 Fe 0.1 Ti 0.07 O 2 , where the localized chemistry and cationic potential can be simultaneously adjusted. Specifically, it can deliver a remarkable capacity of 148.9 mAh g −1 at a current density of 0.1 C, and can realize an outstanding cycling stability with a capacity retention of 87.2% after 1000 cycles at 5 C. It is indicated that the local chemical distribution of oxygen is regulated by doped hard acid metal ions to enhance structural stability, while constructing a biphasic high entropy structure can mitigate structural strain and enhance sodium ion diffusion kinetics. The full cell provides an impressive energy density of 282.8 Wh kg −1 at 34.9 W kg −1 , demonstrating feasibility for practicability.