Fundamentals of Ion‐Exchange Synthesis and Its Implications in Layered Oxide Cathodes: Recent Advances and Perspective

Abstract Layered oxide cathodes such as Ni‐rich ternary and Li‐rich layered cathode materials have been widely used for lithium‐ion batteries owing to their excellent Li⁺ transport properties, high energy density, and relatively low cost. However, such layered cathode materials synthesized by high‐temperature sintering face inherent issues such as low structural stability, irreversible migration of transition metal ions, and irreversible redox reactions of oxygen anions. To make a breakthrough from the perspective of material synthesis, a new ion‐exchange synthesis has emerged in recent years, which is a promising strategy for synthesis of Li‐ion cathodes. Herein, the fundamentals of ion‐exchange synthesis and their implications in layered oxide cathodes for lithium‐ion batteries is presented. Specifically, ion‐exchange synthesis and mechanisms of ion exchange are introduced in detail, followed by a discussion of the reduction of synthetic temperature, the synthesis of novel crystal structures, the inhibited migration of transition metal ions, the increased reversibility of anionic redox, and the optimized surface reconstruction. Finally, a summary and outlook is provided for ion‐exchange synthesis of layered oxide cathodes for lithium‐ion batteries. It is anticipated that this ion‐exchange synthesis will facilitate the commercialization of high‐performance cathode materials for next generation Li‐ion batteries.