A high-quality Ni1/3Fe1/3Mn1/3(OH)2 precursor typically targets specific morphological and structural characteristics to ensure smooth solid-state calcination with sodium salts (e.g., Na2CO3): (1) Morphology: Highly spherical, dense secondary particles composed of tightly packed, plate-like or needle-like primary crystals. (2) Particle Size Distribution: Typically controlled within a narrow range, such as a D50 around 4–8 um (resulting in a final lithiated/sodiated cathode D50 of roughly 7–10 um). (3) Tap Density: Generally targeted above 1.2–1.5 g/cm³ to ensure the final cathode exhibits the high volumetric energy density required for commercial cells. (4) Crystal Structure: It crystallizes in a β-Ni(OH)2-type hexagonal structure, where Fe^{2+/3+} and Mn^{2+} successfully substitute into the nickel hydroxide host lattice.

To transition from the precursor powder to the active cathode material (NaNi1/3Fe1/3Mn1/3O2), the powder undergoes high-temperature calcination:

Sintering Conditions: The precursor is intimately blended with a sodium source and fired in a roller hearth kiln or tube furnace at temperatures ranging from 750°C to 900°C under air or oxygen.

Structural Outcome: Depending on the exact sintering temperature and cooling profile, it forms an O3-type or P2-type layered structure. The O3 phase offers higher initial discharge capacities (typically around 120–135 mAh/g), while the P2 phase generally delivers superior rate capability.