Tuning Lattice Ordering Degree to Enable Controlled Interlayer Slip in Ultra‐Stable O3‐Type Layered Cathodes for Sodium‐Ion Batteries

ABSTRACT O3‐type sodium layered oxide cathodes suffer from irreversible phase transition induced by excessive interlayer slip during the de‐sodiation process, resulting in accelerated structure degradation. Herein, we address this issue by tuning the lattice ordering degree in layered oxides via configurational entropy (ΔS conf ) modulation. Results show that the quasi‐high‐entropy layered oxide (ΔS conf = 1.49 R) features a semi‐ordered covalent lattice with an ordered Mn‐O honeycomb covalent sublattice, while other transition metal (TM) atoms are disordered at the remaining sites. This unique covalent lattice exhibits a moderate electrostatic interaction between TMO 2 layers, thus yielding an intermediate interlayer slip energy barrier, enabling effective stress release through controlled interlayer slip, and facilitating a reversible O3‐P3‐O3 phase transition, outperforming medium‐entropy ordered (1.04 R) and high‐entropy disordered (1.60 R) counterparts. Consequently, the optimized quasi‐high‐entropy cathode exhibits remarkable cycling stability (84.4% capacity retention after 1000 cycles at 5 C), and a 1.25 Ah pouch cell retains 86.9% of its initial capacity after 500 cycles at 2 C. This work further elucidates that ΔS conf regulates phase transition reversibility via tuning lattice ordering degree, establishing it as a key descriptor for the rational design of high‐performance sodium layered oxide cathodes.