Review on the synthesis on Li-rich layered oxide cathodes

Abstract

The bottleneck in enhancing the volumetric/gravimetric energy density of batteries lies in the exploration of cathode materials. Li-rich layered oxides (LLOs) have emerged as a focal point in recent research on cathode materials due to their exceptionally high specific capacity, exceeding 250 mAh g-1. However, the evolution process of reactants during the synthesis of LLOs remains unclear. To achieve controllable preparation of LLOs, this review first explores the lithiation reaction process based on the mechanism and kinetic constraints of solid-phase reactions. Subsequently, phase transitions, elemental valence changes, ion diffusion and migration paths, and the evolution of particle morphology throughout the calcination process of LLOs are comprehensively analyzed. The phenomena occurring at various microscopic levels are systematically elucidated. Furthermore, this review discusses the key factors on affecting the lithiation reaction, such as precursor species, lithium sources, sintering atmospheres, and sintering procedures. Based on these understandings, the relevant strategies have been proposed to modulate reaction pathways. This information provides a valuable guidance for the controlled synthesis of LLOs, thereby accelerating the commercialization of LLO cathode materials for next-generation Li-ion batteries.