Coupling of\nOxygen Dimer and Trapped O<sub>2</sub> with Strong Magnetic\nFrustration in Layered Li-rich Cathodes

Anion redox in layered Li-rich cathodes\nprovides a high capacity\nbut triggers a series of cascading issues. Current research predominantly\nfocuses on how oxygen species participate in redox and how transition\nmetals move, often ignoring the influence of magnetic frustration.\nThis work systematically investigates the potential link between the\nevolution of magnetic frustration, structural evolution and oxygen\nredox in honeycomb Li<sub>2</sub>RuO<sub>3</sub>. Our findings indicate\nthat the phase transition from <i>C</i>2/<i>c</i> to <i>R</i>3 exacerbates the magnetic\nfrustration during Ru oxidation. Subsequently, during oxygen oxidation,\nthe strong magnetic frustration drives the generation of (O<sub>2</sub>)<sup><i>n</i>−</sup> and trapped O<sub>2</sub>,\nwhich serves to relieve and eventually eliminate the magnetic frustration.\nThis (O<sub>2</sub>)<sup><i>n</i>−</sup>/O<sub>2</sub> formation mechanism, termed “magnetic-frustration-driven\nmechanism”, provides a plausible explanation for the formation\nof trapped O<sub>2</sub> in the systems with strong covalent TM–O\nbonds. Accordingly, we emphasize that improvement strategies should\nnot only enhance the covalent TM–O bonds but also relieve strong\nmagnetic frustration.