Reconstructed Perovskite Layers Regulate Surface-Oxygen Dimerization States Enabling Reversible Anionic Redox in Li-Rich Layered Oxides.
basic_science · Level V
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- Record sourced from PubMed, PMID 41492978.
- Also identified by DOI 10.1021/acsnano.5c21117.
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Abstract
Li-rich layered oxides are regarded as promising next-generation cathodes because their additional oxygen redox enables ultrahigh capacities (>250 mAh g<sup>-1</sup>). However, the irreversibility of oxygen redox triggers oxygen loss and structural degradation during cycling, resulting in severe voltage decay and capacity loss. To address this issue, we introduce a perovskite-type PrMO<sub>3-<i>x</i></sub> layer on the Li<sub>1.2</sub>Ni<sub>0.2</sub>Mn<sub>0.6</sub>O<sub>2</sub> surface to modulate the oxygen-oxidation end point from molecular O<sub>2</sub> to superoxide (O<sub>2</sub><sup>-</sup>). Specifically, the PrMO<sub>3-<i>x</i></sub> layer traps migrating O-O dimers via intrinsic O vacancies and promotes electron donation from adjacent Mn cations, thereby reducing the escaping O<sub>2</sub> into O<sub>2</sub><sup>-</sup> species. This suppresses excessive oxygen oxidation and significantly improves the reversibility and kinetics of oxygen redox. Functioning as such a passivating interphase, the PrMO<sub>3-<i>x</i></sub> layer markedly stabilizes the cathode surface over prolonged cycling, inhibiting the layered-to-spinel/rock-salt phase transition and fostering a robust cathode-electrolyte interphase (CEI). Consequently, the modified PrMO@LRNM cathodes achieve 93% capacity retention with only 1.4 mV per cycle voltage decay. This perovskite-coating strategy is readily extendable to other high-voltage, Co-lean/free cathodes.