Comparative study of hydrothermal and co-precipitation routes for synthesizing Ni x Mn y Co 1− x − y (OH) ₂ precursors toward NMC cathode materials

The nature of Ni x Mn y Co 1− x − y (OH) 2 precursors and their impact on the transformation into LiNi x Mn y Co 1− x − y O 2 (NMC) remain debatable and are crucial for large-scale production. In this investigation, hydrothermal and co-precipitation synthesis routes were compared to produce hydroxide precursors and NMC cathode materials. To the best of our knowledge, no direct comparison between the two methods has been reported, leaving gaps in the literature regarding the advantages of each. The differences in the crystalline phase, morphology, and lattice parameters of the Ni x Mn y Co 1− x − y (OH) 2 and LiNi x Mn y Co 1− x − y O 2 materials were evaluated from X-ray diffraction and morphological characterizations. The results have demonstrated that each synthesis route yields structures with distinct features that affect the electrochemical performance of the NMC cathode material. The findings revealed that a single material can exhibit different structures under different synthesis conditions; for instance, particles with a hexagonal structure in space group 7.8 nm crystallite size were obtained by hydrothermal synthesis. In comparison, a regular packing of particles with a diameter of around 0.9 nm crystallite size was obtained, forming a turbostratic structure in the case of the coprecipitation route. Consequently, these synthesis-driven structural variations directly dictate the electrochemical performance of the final cathode materials, demonstrating that precursor synthesis conditions are critical for tailoring NMC performance.