Ni-rich layered cathodes for lithium-ion batteries: From challenges to the future

Extending the limited driving range of current electric vehicles (EVs) necessitates the development of highenergy-density lithium-ion batteries (LIBs) for which Ni-rich layered LiNi1_x_yCoxMnyO2 and LiNi1_x_yCoxAlyO2 cathodes are considered promising cathode candidates. Although the capacity and cost of current LIBs are competitive, a further increase in capacity and reduction in cost are required for next-generation EVs. These performance enhancements can be achieved by increasing the Ni content of layered cathodes. However, enhancements in performance are obtained (using this approach) at the expense of cycling performance and thermal stability, hindering the practical application of these Ni-rich layered cathodes. In this review, the performance limitations of Ni-rich layered cathodes are explored in terms of their surface structural degradation and mechanical failure, as well as the mechanisms of these phenomena. Strategies developed to counter the structural degradation and mechanical failure of Ni-rich layered cathodes through surface stabilization, compositional optimization, microstructural engineering, and cation ordering are evaluated. Finally, future research directions and limitations of Ni-rich layered cathodes are discussed.