Lithium-rich cathode materials are regarded as one of the most promising candidates for high energy lithium-ion batteries delivering reversible capacity of 300 mA·h/g, which are better than the commercial cathode materials. However, some drawbacks of lithium-rich cathode materials (i.e., low initial Coulombic efficiency, voltage decay and capacity decay) affect the practical application. In this review, we represented recent studies on two types lithium-rich cathode materials, i.e. lithium-rich Mn-based cathode materials and lithium-rich cation disordered cathode materials, introduced the crystal structure, cation redox and anion redox mechanisms of these lithium-rich cathode materials in detail, discussed the drawbacks of the materials and some sources of these drawbacks, and summarized the performance improvement, thus providing the theoretical guidance and technical support for future research of lithium-rich cathode materials.

Phase transition is common during (de)-intercalating layered sodium oxides, which directly affects the structural stability and electrochemical performance. However, the artificial control of phase transition to achieve advanced sodium-ion batteries is lacking, since the remarkably little is known about the influencing factor relative to the sliding process of transition-metal slabs upon sodium release and uptake of layered oxides. Herein, we for the first time demonstrate the manipulation of oxygen vacancy concentrations in multinary metallic oxides has a significant impact on the reversibility of phase transition, thereby determining the sodium storage performance of cathode materials. Results show that abundant oxygen vacancies intrigue the return of the already slide transition-metal slabs between O3 and P3 phase transition, in contrast to the few oxygen vacancies and resulted irreversibility. Additionally, the abundant oxygen vacancies enhance the electronic and ionic conductivity of the Na_0.9Ni_0.3Co_0.15Mn_0.05Ti_0.5O₂ electrode, delivering the high initial Coulombic efficiency of 97.1%, large reversible capacity of 112.7 mAh∙g⁻¹, superior rate capability upon 100 C and splendid cycling performance over 1, 000 cycles. Our findings open up new horizons for artificially manipulating the structural evolution and electrochemical process of layered cathodes, and pave a way in designing advanced sodium-ion batteries.