Unravelling the growth mechanism of hierarchically structured Ni1/3Co1/3Mn1/3(OH)2 and their application as precursors for high-power cathode materials

- Hierarchical architectured Ni1/3Co1/3Mn1/3(OH)2 are prepared in a CSTR.
- A possible growth mechanism of hierarchical structured precursors is proposed.
- Electrochemical performances are greatly affected by the hierarchical structure.

A hydroxide co-precipitation method is used to synthesize transition metal hydroxide (Ni1/3Co1/3Mn1/3(OH)2), which is the precursor for layer-structured LiNi1/3Co1/3Mn1/3O2. The optimum pH range for the preparation of Ni1/3Co1/3Mn1/3(OH)2 using a continuous stirred-tank reactor is calculated by taking into account the underlying chemical equilibria. The entire growth process of the Ni1/3Co1/3Mn1/3(OH)2 particles is investigated by monitoring the structure, morphology, particle size distribution, and tap density as a function of the reaction time. The results confirm that the co-precipitation reaction in the presence of ammonia started with the formation of crystal nuclei and (001) plane dominated nanosheets. The reaction ended with spherical and dense hydroxide precursors. The crystal growth mechanism was interpreted during the co-precipitation process, which involved the quick nucleation of primary particles followed by its slow aggregation and crystallization. The electrochemical properties of the final cathode materials with different morphologies are also studied. The results show that the electrochemical performances of the final LiNi1/3Co1/3Mn1/3O2 are strongly affected by the hierarchical structure of Ni1/3Co1/3Mn1/3(OH)2.

A possible growth mechanism of hierarchical structured Ni1/3Co1/3Mn1/3(OH)2 precursors is proposed, and the effect of physicochemical properties of hydroxide precursors on the electrochemical features of the final positive electrode materials are also investigated.134