Multiorbital bond formation for stable oxygen-redox reaction in battery electrodes
Multiorbital bond formation for stable oxygen-redox reaction in battery electrodes
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DOI：
10.1039/c9ee04197d
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发表时间：
2020-05
影响因子：
32.5
通讯作者：
T. Sudayama;K. Uehara;T. Mukai;D. Asakura;Xiang-Mei Shi;Akihisa Tsuchimoto;Benoit Mortemard de Boisse;T. Shimada;Eriko Watanabe;Y. Harada;M. Nakayama;M. Okubo;A. Yamada
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文献类型：
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作者：
T. Sudayama;K. Uehara;T. Mukai;D. Asakura;Xiang-Mei Shi;Akihisa Tsuchimoto;Benoit Mortemard de Boisse;T. Shimada;Eriko Watanabe;Y. Harada;M. Nakayama;M. Okubo;A. Yamada
高能量密度电池一直是可持续发展的长期目标，但最先进的锂离子电池的能量密度在一定程度上受到正极材料容量小的限制。虽然利用锂过量过渡金属氧化物的额外氧氧化还原反应是增加容量的一种有吸引力的方法，但到目前为止，对反应机制的原子水平的理解尚未建立。在这里，我们利用体敏感共振非弹性x射线散射光谱结合从头计算，证明了氧2p轨道与过渡金属t2g轨道弱杂化的局域化存在，理论上预测该轨道在氧氧化还原反应中起关键作用。氧氧化后，氧2p轨道上的空穴通过强π回给形成（σ + π）多轨道键或通过氧二聚化形成过氧化物O22−来稳定。接受σ和给予π的过渡金属形成的多轨道键可以引起可逆的氧-氧化还原反应。
High-energy-density batteries have been a long-standing target toward sustainability, but the energy density of state-of-the-art lithium-ion batteries is limited in part by the small capacity of the positive electrode materials. Although employing the additional oxygen-redox reaction of Li-excess transition-metal oxides is an attractive approach to increase the capacity, an atomic-level understanding of the reaction mechanism has not been established so far. Here, using bulk-sensitive resonant inelastic X-ray scattering spectroscopy combined with ab initio computations, we demonstrate the presence of a localized oxygen 2p orbital weakly hybridized with transition metal t2g orbitals that was theoretically predicted to play a key role in oxygen-redox reactions. After oxygen oxidation, the hole in the oxygen 2p orbital is stabilized by the generation of either a (σ + π) multiorbital bond through strong π back-donation or peroxide O22− through oxygen dimerization. The multiorbital bond formation with σ-accepting and π-donating transition metals can thus lead to reversible oxygen-redox reaction.