Modulating Phase Angle Variations of O3‐Type High‐Entropy Layered Sodium Oxide for Practical Sodium‐Ion Cylindrical Battery

Abstract High‐entropy oxides, with their diverse compositions and entropy‐stabilized structures, have emerged as promising candidates for sodium‐ion battery cathodes. However, phase transitions in these materials are highly sensitive to the specific transition metal composition, and effective design strategies remain underdeveloped. Herein, a six‐element high‐entropy layered oxide cathode, O3‐Na _0.9 Ni _0.3 Fe _0.1 Zn _0.1 Cu _0.05 Mn _0.3 Ti _0.15 O ₂ , is reported in which the incorporation of Zn and Cu not only alters the electronic structure but also affects the formation angle of desired OP2 phase. By fine‐tuning Zn/Cu ratio, we optimize the phase transition behavior of high‐entropy layered oxides, significantly enhancing structural stability and electrochemical performance. This material delivers a high specific capacity of 146.9 mAh g ⁻¹ with superior cycling performance (80.4% capacity retention after 500 cycles). Furthermore, utilizing the as‐prepared cathode and commercial hard carbon anode, 1.1 Ah cylindrical cells successfully demonstrated high initial Coulombic efficiency of 92% and rapid charge and discharge rates up to 5C, retaining 93.6% of the capacity. Notably, these cylindrical cells exhibit excellent cycling stability with capacity retention of 86% after 300 cycles.