Rational Design of High‐Entropy Cathodes to Optimize Fast Charging Performance in Sodium‐Ion Batteries

Abstract Sodium‐ion batteries hold significant potential for fast‐charging applications due to the larger size of sodium ions compare to lithium ions, which inherently enhances ionic mobility. O3‐type sodium‐ion batteries, in particular, attract attention for their high specific energy. However, challenges such as O3 phase transitions, stability under high current densities, air stability, and rate performance persist. Here, a novel O3‐type cathode is designed, Na _0.9 Ni _0.25 Zn _0.07 Fe _0.28 Co _0.08 Mn _0.15 Ti _0.17 O ₂ (NZFCMT), using Ni‐Fe‐Mn oxides and cation‐assisted prediction to achieve phase transition‐free performance under high current densities. Failure mechanisms are investigated using HAADF‐STEM and XRD, identifying a comprehensive mechanism for crystal enhancement. The material achieves a specific capacity of 101.2 mAh·g⁻¹ at 10C and stable cycling at 50C, with 73.7% capacity retention after 1000 cycles. Additionally, its air and thermal stability improve significantly. Full cells validate its practical potential, offering a new approach for fast‐charging cathodes and addressing failure mechanisms in rapid cycling.