Nucleation regulation and mechanism of precursors for nickel cobalt manganese-based cathode materials in lithium-ion batteries

Abstract

Nickel cobalt manganese-based cathode materials (NCMs) have emerged as key representatives in lithium-ion power batteries due to their high energy and power densities. The layered crystal structure of NCMs undergoes topological transformation from hydroxide precursor materials crystals. Therefore, the electrochemical performance of NCMs is directly influenced by factors such as particle size distribution, sphericity, and morphology of primary and secondary particles of precursor materials. The co-precipitation method is widely employed in laboratory and industry to produce batch precursor materials with uniform composition, adjustable structure, and high tap density. However, the co-precipitation process involves numerous adjustable parameters, and there exist significant variations in the growth parameters of precursors with different compositions and even different particle sizes within the same composition, resulting in poor characteristics such as bad sphericity, poor crystallinity, and low tap density. Addressing the need for controlled co-precipitation of nickel cobalt manganese-based precursors, this review began with an exposition on the basic theory of co-precipitation, elaborating on the principle of regulating precipitation rate and uniformity of Ni–Co–Mn elements through complexation. The heterogeneous nucleation (growth), homogeneous nucleation (independent nucleation), and the coexistence of two nucleation modes induced by different supersaturation of precipitates were explained according to different nucleation dominant modes. The growth theory of hexagonal nanosheet and rod-shaped primary particles was introduced from the perspective of preferential growth, while analyzing the growth pattern of secondary particle aggregates in terms of minimizing surface energy and following dissolving-recrystallization. From the viewpoint of practical production and application, this study comprehensively investigated adjustable parameters of the co-precipitation reaction process, including pH value, total ammonia concentration, solid content, reaction time, reaction temperature, base solution volume, stirring rate, tank reactor structure, aging time, reaction atmosphere, and drying atmosphere. The impact of varying each parameter from low to high on the nucleation of the co-precipitation reaction process and the physicochemical properties of precursors was extensively discussed. This systematic review contributes to a deeper understanding of the precursor nucleation process, facilitating the further development of relevant theories towards the advancement of products such as lithium-rich manganese-based precursors, single crystal precursors, and radially arranged texture precursors.