Molecular Orbital Principles of Oxygen-Redox Battery Electrodes

作者：Okubo Masashi; Yamada Atsuo^*

来源：ACS Applied Materials & Interfaces, 2017, 9(42): 36463-36472.

DOI：10.1021/acsami.7b09835

• battery
• cathode
• transition-metal oxides
• oxygen-redox reaction
• molecular-orbital method
• orphaned oxygen orbital

Lithium-ion batteries are key energy-storage devices for a sustainable society. The most widely used positive electrode materials are LiMO2 (M: transition metal), in which a redox reaction of M occurs in association with Li+ (de)intercalation. Recent developments of Li-excess transition-metal oxides, which deliver a large capacity of more than 200 mAh/g using an extra redox reaction of oxygen, introduce new possibilities for designing higher energy density lithium-ion batteries. For better engineering using this fascinating new chemistry, it is necessary to achieve a full understanding of the reaction mechanism by gaining knowledge on the chemical state of oxygen. In this review, a summary of the recent advances in oxygen-redox battery electrodes is provided, followed by a systematic demonstration of the overall electronic structures based on molecular orbitals with a focus on the local coordination environment around oxygen. We show that a 7r-type molecular orbital plays an important role in stabilizing the oxidized oxygen that emerges upon the charging process. Molecular orbital principles are convenient for an atomic-level understanding of how reversible oxygen-redox reactions occur in bulk, providing a solid foundation toward improved oxygen-redox positive electrode materials for high energy-density batteries.

• 出版日期2017-10-25