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Oxygen redox chemistry without excess alkali-metal ions in Na2/3[Mg0.28Mn0.72]O2
Nature Chemistry ( IF 21.8 ) Pub Date : 2018-01-22 , DOI: 10.1038/nchem.2923
Urmimala Maitra , Robert A. House , James W. Somerville , Nuria Tapia-Ruiz , Juan G. Lozano , Niccoló Guerrini , Rong Hao , Kun Luo , Liyu Jin , Miguel A. Pérez-Osorio , Felix Massel , David M. Pickup , Silvia Ramos , Xingye Lu , Daniel E. McNally , Alan V. Chadwick , Feliciano Giustino , Thorsten Schmitt , Laurent C. Duda , Matthew R. Roberts , Peter G. Bruce

The search for improved energy-storage materials has revealed Li- and Na-rich intercalation compounds as promising high-capacity cathodes. They exhibit capacities in excess of what would be expected from alkali-ion removal/reinsertion and charge compensation by transition-metal (TM) ions. The additional capacity is provided through charge compensation by oxygen redox chemistry and some oxygen loss. It has been reported previously that oxygen redox occurs in O 2p orbitals that interact with alkali ions in the TM and alkali-ion layers (that is, oxygen redox occurs in compounds containing Li+–O(2p)–Li+ interactions). Na2/3[Mg0.28Mn0.72]O2 exhibits an excess capacity and here we show that this is caused by oxygen redox, even though Mg2+ resides in the TM layers rather than alkali-metal (AM) ions, which demonstrates that excess AM ions are not required to activate oxygen redox. We also show that, unlike the alkali-rich compounds, Na2/3[Mg0.28Mn0.72]O2 does not lose oxygen. The extraction of alkali ions from the alkali and TM layers in the alkali-rich compounds results in severely underbonded oxygen, which promotes oxygen loss, whereas Mg2+ remains in Na2/3[Mg0.28Mn0.72]O2, which stabilizes oxygen.



中文翻译:

Na 2/3 [Mg 0.28 Mn 0.72 ] O 2中没有过量碱金属离子的氧还原化学

对改进的储能材料的研究表明,富含锂和钠的插层化合物有望成为高容量阴极。它们的容量超过了碱金属离子的去除/重新插入和过渡金属(TM)离​​子的电荷补偿所期望的容量。通过氧气氧化还原化学的电荷补偿和一些氧气损失来提供额外的容量。以前有报道说,氧的氧化还原发生在与TM和碱离子层中的碱离子相互作用的O 2 p轨道上(也就是说,氧的氧化还原发生在含有Li + -O(2 p)-Li +相互作用的化合物中) 。Na 2/3 [Mg 0.28 Mn 0.72 ] O 2表现出过剩的容量,在这里我们表明这是由氧的氧化还原引起的,即使Mg 2+驻留在TM层中,而不是碱金属(AM)离子也存在,这表明不需要过量的AM离子来激活氧的氧化还原。我们还表明,与富含碱的化合物不同,Na 2/3 [Mg 0.28 Mn 0.72 ] O 2不会失去氧。从富含碱的化合物中的碱层和TM层中提取碱离子会导致严重的键合氧不足,从而促进氧损失,而Mg 2+保留在Na 2/3 [Mg 0.28 Mn 0.72 ] O 2中,从而使氧稳定。

更新日期:2018-01-22
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