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

The O3-NaNi_0.5Mn_0.5O₂ 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_0.796Ni_0.3Mn_0.47Al_0.03Zn_0.03Fe_0.1Ti_0.07O₂, 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.