Ni-rich cathode materials with concentration gradients for high-energy and safe lithium-ion batteries: A comprehensive review

Nickel-rich (Ni-rich) cathode materials with concentration gradients have emerged as promising candidates for high-energy and safe lithium-ion batteries (LIBs). These cathode materials offer enhanced energy densities and improved electrochemical performances compared to conventional cathode materials, making them ideal for various applications ranging from portable electronics to electric vehicles and grid storage systems. This paper provides a comprehensive review of the fundamental aspects of material design, recent advancements, synthesis strategies, as well as effects of Ni-rich cathode materials with concentration gradient structure on overall battery performance. The discussion encompasses the underlying principles governing concentration gradients in Ni-rich cathode materials, including their effects on elemental composition, morphology, crystal lattice parameters, thermal stability, diffusion, and electrochemical properties. Furthermore, the insights into the current state-ofthe-art, challenges, and future directions in the field of Ni-rich cathode materials with concentration gradients for high-energy and safe LIBs are also discussed here. By synthesizing the latest research findings and identifying research gaps and opportunities, this paper aims to catalyze further advancements in battery materials science and contribute to the realization of sustainable energy storage technologies.