Advances in reactive co-precipitation technology for preparing high-performance cathodes

Reactive crystallization plays an essential role in the synthesis of high-quality precursors with a narrow particle size distribution, dense packing, and high sphericity. These features are beneficial in the fabrication of high-specific-capacity and long-cycle-life cathodes for lithium-ion and sodium-ion batteries. However, in industrial production, designing and scaling-up crystallizers involves the use of semi-empirical approaches, making it challenging to satisfactorily meet techno-economic requirements. Furthermore, there is still a lack of in-depth knowledge on the theoretical models and technical calculations of the current co-precipitation process. This review elaborates on critical advances in the theoretical guidelines and process regulation strategies using a reactive crystallizer for the preparation of precursors by co-precipitation. The research progress on the kinetic models of co-precipitation reactive crystallization is presented. In addition, the regulation strategies for the reactive crystallization process of lithium-ion ternary cathodes are described in detail. These include the influence of different reactive crystallizer structures on the precursor's morphology and performance, the intelligent online measurement of efficient reactive crystallizers to ensure favorable conditions of co-precipitation, and preparing the precursor with a high tap density by increasing its solid holdup. A controllable reactive crystallization process is described in terms of the structural design with concentration gradient materials and bulk gradient doping of advantageous elements (such as magnesium ion) in lithium-ion cathodes and the fabrication of sodium-ion cathodes with three typical materials—Prussian blue analogues, transition metal oxides, and polyanionic phosphate compounds being involved.