0.71% Lattice‐Mismatched Intergrowth Achieves 2000‐Cycle Stability in O3‐Type Na‐Layered Oxide Cathodes

ABSTRACT O‐type sodium‐based layered oxide cathodes show strong practical applicability due to their high theoretical capacity. However, the narrow ion diffusion channels in the O‐type framework often lead to poor cycling stability, posing a challenge long‐term durability over thousands of cycles. Herein, we establish the Bramfitt lattice mismatch value ( δ interplanar ) as a key quantitative descriptor for intergrowth phase stability and a lattice‐matched O3/O'3 intergrowth structure is proposed, which exhibits superior cycling stability. The ultralow Bramfitt lattice mismatch value ( δ interplanar = 0.71%) in Na + ‐active facets enables tight integration of rigid O3 and flexible O′3 phases, forming a robust rigid‐flexible‐rigid structure. This design effectively mitigates TM slab gliding, resulting in a pure P‐type solid solution region of 86.7% during charge/discharge and a minimal volume expansion of only 2.39%. Moreover, the stable framework suppresses transition metal dissolution and parasitic anion redox, ensuring highly reversible Na + insertion/extraction. The combination of above factors results in an outstanding cycling stability with 79.7% capacity retention after 2000 cycles, significantly outperforming conventional O‐type materials. This work decouples the quantitative role of lattice mismatch in intergrowth phase stability and provides a highly compatible cathode, offering valuable guidance for the construction of high‐performance sodium‐ion batteries geared toward practical large‐scale energy storage.