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

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 Na0.67Fe0.2Mn0.8O2@Oxygen-Free derived from conventional P2-type Na0.67Fe0.2Mn0.8O2 via oxygen-free re-sintering treatment, and further introduce trace Cu/Ti into the transition metal layer to obtain Na0.67Fe0.2Mn0.76Cu0.02Ti0.02O2. 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.