Ultra‐High Nickel Oxides as Cathode Materials for High‐Energy Lithium‐Ion Batteries

Ultra‐high nickel layered oxides are currently among the mainstream cathode materials for lithium‐ion batteries (LIBs), having garnered extensive research and rapid development due to their high capacity. This review article defines ultra‐high nickel oxides with a nickel content of ≥0.9 among transition metal components and proceeds based on this definition. Although high‐nickel oxide cathode materials have undergone decades of development, the pursuit of increased capacity in ultra‐high nickel oxides inevitably leads to compromised capacity retention, thermal stability, and unavoidable structural degradation, thereby hindering their progression. The review article focuses on summarizing the main challenges currently faced by ultra‐high nickel oxides as cathode materials for lithium‐ion batteries and as well as the mainstream modification measures. Finally, it is pointed out that the future research on ultra‐high nickel oxides should focus on high‐entropy modification, adaptation to extreme conditions, and the exploration of new preparation and modification methods. At the same time, efforts should be grounded in practical considerations and guided by target performance, aiming to improve various aspects of material performance for different application fields without compromising the high capacity inherent to ultra‐high nickel oxide cathodes.