Recent progress in Ni-rich layered oxides and related cathode materials for Li-ion cells

Undoubtedly, the enormous progress observed in recent years in the Ni-rich layered cathode materials has been crucial in terms of pushing boundaries of the Li-ion battery (LIB) technology. The achieved improvements in the energy density, cyclability, charging speed, reduced costs, as well as safety and stability, already contribute to the wider adoption of LIBs, which extends nowadays beyond mobile electronics, power tools, and electric vehicles, to the new range of applications, including grid storage solutions. With numerous published papers and broad reviews already available on the subject of Ni-rich oxides, this review focuses more on the most recent progress and new ideas presented in the literature references. The covered topics include doping and composition optimization, advanced coating, concentration gradient and single crystal materials, as well as innovations concerning new electrolytes and their modification, with the application of Ni-rich cathodes in solid-state batteries also discussed. Related cathode materials are briefly mentioned, with the high-entropy approach and zero-strain concept presented as well. A critical overview of the still unresolved issues is given, with perspectives on the further directions of studies and the expected gains provided.