Revealing the Role\nof Ammonia in the Rapid Crystallization\nKinetics for Ni-Rich Hydroxide Precursors via Microreactors

The morphology and microstructure of precursors are the\nkey to\nthe preparation of high-quality NCM cathodes due to their inheritance\nrelationship. However, a large amount of sulfate exists in the precursors,\nto the detriment of the electrochemical performance of the Ni-rich\ncathode materials. Herein, an effective method for sulfate reduction\nwas proposed for the synthesis of Ni<sub>0.90</sub>Co<sub>0.05</sub>Mn<sub>0.05</sub>(OH)<sub>2</sub> precursor by adding 0.24 M ammonia\nin the microreactor. The less sulfate in the Ni(OH)<sub>2</sub> with\nammonia system is attributed to the higher formation energy of sulfate\nadsorption (<i>E</i><sub>Ni(OH)<sub>2</sub>‑am‑SO<sub>4</sub><sup>2–</sup></sub> = 7.483 eV vs <i>E</i><sub>Ni(OH)<sub>2</sub>‑SO<sub>4</sub><sup>2–</sup></sub> = 3.451 eV). The results demonstrated that ammonia can promote\nthe growth of primary particles (81.5 nm) and reduce the content of\nimpurity sulfate from 0.80 to 0.28% in the precursors. Moreover, the\nprepared cathode materials exhibit a high specific capacity of 190.4\nmAh g<sup>–1</sup> at 1C and superior Li<sup>+</sup> diffusion\ncoefficients. This study sheds light on the role of ammonia in rapid\ncoprecipitation and provides guidance for the rapid synthesis process\nof Ni-rich cathodes.