Kang Seongkoo, Choi Dayeon, Lee Hakwoo, Choi Byungjin, Kang Yong-Mook
Department of Materials Science and Engineering, Korea University, Seoul, 02841, Republic of Korea.
Department of Battery-Smart Factory, Korea University, Seoul, 02841, Republic of Korea.
Adv Mater. 2023 Oct;35(43):e2211965. doi: 10.1002/adma.202211965. Epub 2023 Jun 29.
Li-rich cathodes are extensively investigated as their energy density is superior to Li stoichiometric cathode materials. In addition to the transition metal redox, this intriguing electrochemical performance originates from the redox reaction of the anionic sublattice. This new redox process, the so-called anionic redox or, more directly, oxygen redox in the case of oxides, almost doubles the energy density of Li-rich cathodes compared to conventional cathodes. Numerous theoretical and experimental investigations have thoroughly established the current understanding of the oxygen redox of Li-rich cathodes. However, different reports are occasionally contradictory, indicating that current knowledge remains incomplete. Moreover, several practical issues still hinder the real-world application of Li-rich cathodes. As these issues are related to phenomena resulting from the electronic to atomic evolution induced by unstable oxygen redox, a fundamental multiscale understanding is essential for solving the problem. In this review, the current mechanistic understanding of oxygen redox, the origin of the practical problems, and how current studies tackle the issues are summarized.
富锂正极因其能量密度优于锂化学计量比正极材料而受到广泛研究。除了过渡金属氧化还原反应外，这种引人注目的电化学性能还源于阴离子亚晶格的氧化还原反应。这种新的氧化还原过程，即所谓的阴离子氧化还原，或者更直接地说，在氧化物的情况下是氧氧化还原，与传统正极相比，几乎使富锂正极的能量密度提高了一倍。大量的理论和实验研究已经彻底确立了目前对富锂正极氧氧化还原的理解。然而，不同的报道偶尔会相互矛盾，这表明目前的知识仍然不完整。此外，几个实际问题仍然阻碍着富锂正极的实际应用。由于这些问题与不稳定氧氧化还原引起的从电子到原子演化的现象有关，因此从根本上进行多尺度理解对于解决该问题至关重要。在这篇综述中，总结了目前对氧氧化还原的机理理解、实际问题的根源以及当前研究如何解决这些问题。
