Atomic-Scale Intergrowth Regulation Enables Long-Cycling Zero-Strain Sodium Layered Oxide Cathodes

Abstract P2-type layered oxide cathodes feature high median voltage and outstanding cycling stability, but their specific capacity of merely 80 mAh g–1 severely limits practical utility. Conventional P2/O3 biphasic strategies to boost capacity typically sacrifice structural stability or median voltage. In this work, density functional theory calculations identify the thermodynamic phase-ratio boundary for biphasic stability, confirming that limiting sodium-rich O3 phase below 20% suppresses the detrimental O3-P3 transition during cycling. Guided by this, precise transition metal tuning yields an optimal atomically intermixed P2/O3-93 cathode (Na3/4Ni1/3Fe1/12Mn7/12O2). It exhibits pronounced zero-strain behavior, with volume change reduced from 3.7% (O3-type reference) to <1%. It maintains a 3.3 V median voltage, raises capacity by 40% to 112 mAh g–1, and achieves 93% retention after 500 cycles at 1 C. Furthermore, it enables 300 stable cycles in all-solid-state sodium-ion batteries at 30 MPa, offering a viable route for high-performance layered oxide cathodes.