Regulating the Intralayer Cation Disorder in Layered Lithium-Rich Cathodes to Improve Cycle Performance

The Li/Mn ordered structure of lithium-rich (LR) cathodes leads to the heterogeneous Li₂MnO₃ and LiTMO₂ components, readily triggering structural degeneration and performance degradation in long-term cycling. However, the lack of guiding principles for promoting cation disorder within the transition metal (TM) layers has posed a persistent challenge in designing homogeneous layered LR cathodes. Herein, the (Li + Mn)_TM content in the TM layer as a criterion for the design of cation-disordered layered LR cathodes is proposed. The intralayer cation disorder can be achieved by tuning the (Li + Mn)_TM content less than 0.5 combined with incorporating the solute ions with suitable ionic radii. For a multicomponent LR nickel cobalt manganese (LRNCM) oxides system, multiscale structural analyses reveal that cation-disordered layered Li_1.1(Ni_0.6Co_0.1Mn_0.3)_0.9O₂ (LR613) exhibits enhanced compositional homogeneity and higher R $$ m symmetry. The developed LR613 cathode undergoes a solid-solution reaction during Li⁺ deintercalation and mitigates voltage decay during cycling. It is elucidated that intralayer cation disorder effectively alleviates microstrain within the cathode structure and enhances overall structural stability. This comprehensive understanding of the composition-structure-electrochemical behavior relationship inspires the development of durable cation-disordered layered LR cathodes through composition tuning.