In this review, research progress on layered oxide cathodes for SIBs in recent years is summarized, with emphasis on the problems of poor cycle life caused by irreversible phase transition, Jahn–Teller effect and interface deterioration, and several strategies are proposed to alleviate these issues.

High‐capacity layered oxide Ni‐rich cathodes are attractive to enhance the driving‐range of electric vehicles because of its preferential costs. Nevertheless, in Ni‐rich cathodes, there are still many issues such as microcracks generation along grain boundaries and interface side reaction between active substance and electrolyte, resulting in the rapidly deterioration of electrochemical property. Herein, improving the performance of Ni‐based cathodes by structural regulation is summarized. The remaining challenges and outlook are discussed as well. image

Ni-rich cathodes with a radial ordered microstructure have been proved to enhance materials' structural stability. However, the construction process of radial structures has not yet been clearly elaborated. Herein, the formation process of radial structures induced by different doped elements has been systematically investigated. The advanced Electron Back Scatter Diffraction (EBSD) characterization reveals that W-doped materials are more likely to form a low-angle arrangement between crystal planes of the primary particles and exhibit twin growth during sintering than a B-doped cathode. The corresponding High Angle Annular Dark Field-Scanning Transmission Electron Microscopy (HAADF-STEM) analysis further proves that the twin growth induced by W doping can promote the migration of Li⁺. Simultaneously, the W-doped sample reduces the (003) plane surface energy and promotes the retention of the crystal plane, which can effectively alleviate the structural degradation caused by Li⁺ (de)intercalation. At a cut-off voltage of 4.6 V, the W-doped cathode displays a capacity retention rate of 94.1% after 200 cycles at 1C. This work unveils the influence of different element doping on the structure from the perspective of crystal plane orientation within primary particles and points out the importance of the exposure and orientation of the crystal plane of the particles.

Single-crystal Ni-rich cathodes possess prominent structural integrity and thermal stability compared to their poly-crystal counterparts, yet their application at high voltage is hampered by the intragranular cracks that remain intractable for mitigation. Herein, a novel niobium-modified single-crystal LiNi_0.83Co_0.12Mn_0.05O₂ (NCM) cathode, which integrates grain size and lattice regulation superiorities, is designed. The results demonstrate that doped Nb⁵⁺ reduces the surface energies of (001), (012), and (104) faces, followed by the diminution of critical nuclei size and grain size based on the classical nucleation theory. Smaller grain size effectively facilitates the release of internal strain, resulting in fewer planar slips and intragranular cracks inside the niobium-modified cathodes. Moreover, a heterogeneous surface structure derived by Nb⁵⁺ doping acts as a shield to alleviate the deleterious interfacial phase transition. Under a high-voltage of 4.4 V, the 0.5 mol% Nb⁵⁺-doped NCM displays an outstanding discharge capacity (211.3 mA h g⁻¹) at 0.1C, higher capacity retention (155.0 mA h g⁻¹vs. 130.2 mA h g⁻¹) at 1C after 100 cycles and a superior rate capacity (152.3 mA h g⁻¹vs. 118.9 mA h g⁻¹) at 5C in comparison with the pristine material. This bifunctional regulation strategy provides novel insights into the rational design of single-crystal Ni-rich cathodes.