mismatch between the cathode and anode materials (the cathode capacity is nearly an order of magnitude smaller than the anode capacity) has seriously hindered the development of LIBs. [2] Li-rich cathode materials have been regarded as one of the most promising candidates for next-generation cathode materials for rechargeable LIBs owing to their prominent specific capacity. For instance, in Li-rich Mn-based (LRM) cathode materials with the chemical formula xLi 2 MnO 3 ⋅(1 -x)LiTMO 2 (TM = Ni, Mn, Co, etc.), when x = 0.5, in the form of Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 O 2 , the theoretical capacity of the LRM cathode reaches over 250 mA h g −1 for 1 Li + extraction, and ≈378 mA h g −1 for 1.2 Li + extraction. [3] Furthermore, LRM cathodes reduce the use of expensive Co and have the advantages of low cost, environmental friendliness, and high thermal stability. However, LRM cathode materials have inherent issues, such as low initial Coulombic efficiency (ICE), poor rate capacity, and serious voltage fading, which inhibit their further practical applications. [4] These issues need to be immediately addressed to eliminate range and safety anxiety in the electric consumption market. The development of state-of-the-art characterization techniques has brought new understandings of the origins of these problems. [5] In this case, considerable progress has been made in the evolution of LRM cathode structures and its various reaction mechanisms during long-time cycles, the electrochemical activity of anions, and other aspects. In addition, significant advances have also been made in the novel modification methods for promoting the electrochemical performances of LRM cathode materials as well as other branches of Li-rich cathode materials. Herein, we present a comprehensive review of the recent challenges and prospects in high-capacity Li-rich cathode materials. This paper aims to offer a global and critical perspective on Lirich cathode materials for LIBs, as shown in Figure 1, including an in-depth evaluation of degradation mechanisms, the prevailing modification methods and development trends, application, and future opportunities for LRM electrode materials in full-cells and future solid-state batteries. We intend to provide perspectives on the practical development and application of Li-rich cathode materials have attracted increasing attention because of their high reversible discharge capacity (>250 mA h g −1 ), which originates from transition metal (TM) ion redox reactions and unconventional oxygen anion redox reactions. However, many issues need to be addressed before their practical applications, such as their low kinetic properties and inefficient voltage fading. The development of cutting-edge technologies has led to cognitive advances in theory and offer potential solutions to these problems. Herein, a recent in-depth understanding of the mechanisms and the frontier electrochemical research progress of Li-rich cathodes are reviewed. In addition, recent advances associated with various strategies to promot...

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