Abstract: Lithium-rich materials (LRMs) are among the most promising cathode materials toward next-generation Li-ion batteries due to their extraordinary specific capacity of over 250 mAh g⁻¹ and high energy density of over 1 000 Wh kg⁻¹. The superior capacity of LRMs originates from the activation process of the key active component Li₂MnO₃. This process can trigger reversible oxygen redox, providing extra charge for more Li-ion extraction. However, such an activation process is kinetically slow with complex phase transformations. To address these issues, tremendous effort has been made to explore the mechanism and origin of activation, yet there are still many controversies. Despite considerable strategies that have been proposed to improve the performance of LRMs, in-depth understanding of the relationship between the LRMs' preparation and their activation process is limited. To inspire further research on LRMs, this article firstly systematically reviews the progress in mechanism studies and performance improving attempts. Then, guidelines for activation controlling strategies, including composition adjustment, elemental substitution and chemical treatment, are provided for the future design of Li-rich cathode materials. Based on these investigations, recommendations on Li-rich materials with precisely controlled Mn/Ni/Co composition, multi-elemental substitution and oxygen vacancy engineering are proposed for designing high-performance Li-rich cathode materials with fast and stable activation processes.

Key words: Li-rich cathode materials, Activation, Compositional control, Elemental substitution, Chemical treatment