Mitigating the Cooperative Distortion and Phase Transition of P'2 Phase to Prepare Stable Fast-Charghing Layered...

Sodium-ion batteries are promising for large-scale energy storage systems, but simultaneously achieving high capacity, super-fast charging, and long-term cycling remains challenging. Here, we report a P'2-type layered oxide cathode Na_0.67Fe_0.2Mn_0.8O₂@Oxygen-Free derived from conventional P2-type Na_0.67Fe_0.2Mn_0.8O₂ via oxygen-free re-sintering treatment, and further introduce trace Cu/Ti into the transition metal layer to obtain Na_0.67Fe_0.2Mn_0.76Cu_0.02Ti_0.02O₂. The co-doping strategy alleviates phase transition and enhances structural stability. As a result, FMOF-CT delivers a high reversible capacity of 197.76 mAh g^{- 1} at 0.2C and retains 99.35% of its initial capacity after 100 cycles at an ultra-high rate of 20C. Combined in situ characterization methods reveal that the superior kinetic performance originates from faster Na⁺ diffusion, smoother P'2-P2-OP4 phase evolution, and mitigated interlayer slip. Subsequently, neutron powder diffraction is performed to reveal the structure-activity relationship. This work demonstrates an effective structural design for achieving super-fast charging and stable cycling in layered oxide cathodes for sodium-ion batteries.