Oxygen-anchoring high-entropy design boosting anionic redox reversibility in Li-rich layered cathodes

The irreversible oxygen redox (OR) in Li-rich layered cathodes leads to severe structural degradation and voltage decay, particularly under harsh operating conditions. Although high-entropy oxides (HEOs) offer enhanced stability compared to conventional doping modifications, rational element selection for optimizing OR reversibility remains unexplored. Here, we propose an entropy engineering design paradigm for “oxygen-anchoring”, where optimal cation electronegativity (>Mn, 1.55) and d (3d/4d)-p orbital hybridization synergistically enhance transition metal–oxygen (TM–O) covalency and stabilize the O 2p state. Two high-entropy Li-rich layered oxides: Li1.2Mn0.47Ni0.115Co0.115Mg0.02Ti0.02Al0.02Nb0.02Mo0.02O2 (MTANM) and Li1.2Mn0.47Ni0.115Co0.115Mg0.02Ti0.02Cu0.02Nb0.02Mo0.02O2 (MTCNM) were synthesized using partial nano-scale precursors and comparatively evaluated. MTCNM exhibits enhanced electrochemical performance and superior oxygen stability compared to MTANM by replacing Al with higher-electronegativity Cu, which possesses improved orbital overlap with oxygen. Both experiments and density functional theory (DFT) calculations demonstrate that element selection changes the covalency of TM–O through altered electronegativity and d orbitals-p orbitals (d-p) hybridization. Further stepwise screening selected the optimal elemental combination Li1.2Mn0.47Ni0.115Co0.115Cr0.02Cu0.02Nb0.02Mo0.02Ru0.02O2 (CCNMR), which achieved near 100% capacity retention after 150 cycles at 1 C, 50 °C, with its voltage decay effectively suppressed. This work establishes a rational element-screening paradigm for entropy-stabilized OR chemistry in high-energy cathodes.