The Effect of Controlling Strategies of pH and Ammonia Concentration on Preparing Full Concentration Gradient Ni<sub>0.8</sub>Co<sub>0.1</sub>Mn<sub>0.1</sub>(OH)<sub>2</sub> via Coprecipitation in a Pilot‐Scale Reactor
Jihai Duan, Ruchao Zhang, Quanhong Zhu, Hang Xiao, Qingshan Huang
Abstract
Full concentration gradient (FCG)‐Ni 1− x − y Co x Mn y (OH) 2 is generally synthesized via varying the molar ratio of metal ions in feeding flow during coprecipitation. Accordingly, pH and [N] (ammonia concentration) should change with the reaction time given that the optimum pH and [N] are different with variations of x or y . Hence, the effect of the controlling strategies of pH and [N] on preparing the FCG‐precursor is explored, and the mechanism behind is revealed. The FCG‐precursor with the covariation of pH and [N] has the densest and firmest structure, highest tap density (2.115 g mL −1 ), and a well‐ordered layered crystal structure. In addition, its discharge capacity can reach as high as 189.4 mAh g −1 (capacity retention of 96.3%) after 200 cycles at 1 C rate, which is 9.1% and 15.8% higher than FCG‐NCM811 with constant pH, [N], and Homo‐NCM811. The match between pH and [N] is crucial to obtain the favorable FCG‐precursor and ‐NCM811.