The O3-type NaTMO₂ (where TM represents a transition metal) cathode material is highly promising for sodium-ion batteries due to its high theoretical specific capacity and cost-effectiveness. However, its industrialization and commercialization have been hindered by complex phase transitions, sluggish sodium-ion diffusion kinetics, and inhomogeneous stress release within the transition metal layers. In this study, we employ a Zr-doped O3-type NaNi_1/3Fe_1/3Mn_1/3O₂ (NFMZ) cathode material to address these challenges. The incorporation of Zr promotes the growth of the (003) crystal plane, accelerates the kinetic process, increases the sodium-ion diffusion coefficient, and enhances the TM-O bond energy, thereby improving phase transition reversibility and enabling a rapid O3-to-P3 transformation. When assembled into Ah-level pouch-type full-cells with a hard carbon anode, the NFMZ cathode delivers an excellent discharge capacity of 1.76 Ah within a voltage range of 1.5–3.9 V at 0.5 C, and retains 95.63% of its initial capacity after 1000 cycles. More importantly, this work elucidates the mechanism by which Zr doping enhances the electrochemical performance of NFM. The NFMZ cathode also exhibits an enhanced stress release mechanism from the interior to the exterior, effectively mitigating stress accumulation and enabling the stable operation of Ah-level pouch-type full-cells.

Li-rich oxides are considered as promising candidate cathode materials for high-energy Li-ion batteries due to their high specific capacity. However, the widespread adoption of Li-rich materials is hindered because of the lack of a stable surface structure to inhibit interfacial side reactions. In this study, a stable LiF@spinel dual shell was constructed on the surface of Li-rich materials, in which spinel is formed by in situ surface reconstruction, and LiF is bonded to the spinel through the Ni–F bond. The spinel serves as a buffer layer between the LiF coating and the Li-rich oxide, providing a three-dimensional Li-ion diffusion channel to improve the Li-ion diffusion coefficient, while the outer LiF plays a critical role in isolating the cathode from the electrolyte. Under the abovementioned dual effect, the interfacial side reactions of Li-rich materials are inhibited, thereby improving their cycle stability. The obtained LiF@spinel-coated Li-rich cathode exhibits an enhanced capacity retention of 81.5% after 150 cycles at a current density of 2 C, which is better than the pristine Li-rich sample (63.2%). These findings indicate that the construction of the LiF@spinel dual shell is a successful strategy for the modification of Li-rich materials.