Cationic ordering transition in oxygen-redox layered oxide cathodes

Understanding the structural origin of the competition between oxygen 2p and transition -metal 3d orbitals in oxygen-redox (OR) layered oxides is eminently desirable for exploring reversible and high -energy -density Li/Na-ion cathodes. Here, we reveal the correlation between cationic ordering transition and OR degradation in ribbon -ordered P3-Na0.6Li0.2Mn0.8O2 via in situ structural analysis. Comparing two different voltage windows, the OR capacity can be improved approximately twofold when suppressing the in -plane cationic ordering transition. We find that the intralayer cationic migration is promoted by electrochemical reduction from Mn4+ to Jahn-Teller Mn3+ and the concomitant NaO6 stacking transformation from triangular prisms to octahedra, resulting in the loss of ribbon ordering and electrochemical decay. First -principles calculations reveal that Mn4+/Mn3+ charge ordering and alignment of the degenerate e(g) orbital induce lattice -level collective Jahn-Teller distortion, which favors intralayer Mn-ion migration and thereby accelerates OR degradation. These findings unravel the relationship between in -plane cationic ordering and OR reversibility and highlight the importance of superstructure protection for the rational design of reversible OR -active layered oxide cathodes.

Automated summary

The correlation between cationic ordering transition and OR degradation in P3-Na0.6Li0.2Mn0.8O2 is revealed through in situ structural analysis. Suppressing the in-plane cationic ordering transition can improve the OR capacity by approximately twofold. First-principles calculations show that the charge ordering and alignment of the degenerate e(g) orbital induce lattice-level collective Jahn-Teller distortion, promoting intralayer Mn-ion migration and accelerating OR degradation.