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Metal‐Ligand π Interactions in Lithium‐Rich Li 2 RhO 3 Cathode Material Activate Bimodal Anionic Redox
Author(s) -
Zhang Kun,
Jiang Zewen,
Ning Fanghua,
Li Biao,
Shang Huaifang,
Song Jin,
Zuo Yuxuan,
Yang Tonghuan,
Feng Guang,
Ai Xinping,
Xia Dingguo
Publication year - 2021
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.202100892
Subject(s) - redox , materials science , lithium (medication) , cathode , reactivity (psychology) , metal , transition metal , ligand (biochemistry) , oxygen , covalent bond , oxide , oxidation state , inorganic chemistry , chemistry , catalysis , organic chemistry , medicine , biochemistry , alternative medicine , receptor , pathology , metallurgy , endocrinology
Li‐rich oxide (LRO) cathodes that exhibit anionic redox activity can boost the energy density of Li‐ion batteries. Oxygen redox in LROs can originate from the charge compensation of pure O 2p nonbonding (NB) states; however, the high charging voltages cause much safety concerns in practical applications. Exploiting new anionic redox modes that can be used at low voltages is thus imperative. In view of this, a further understanding of the anionic redox behavior with respect to metal‐ligand interactions in LROs is highly desired. In this study, by analyzing the orbital combinations of transition metals (TMs) and O in LROs, the prevalence of π‐type, σ‐type, and NB states is investigated. Highly covalent Li 2 RhO 3 with strong π‐type interactions is selected as a model material. Owing to the closer energy levels of O and Rh and the orbital vacancy of Rh 4+ , oxygen acts as a π‐electron donor to central Rh and exhibits high reactivity in the occupied anti‐bonding state, showing a novel low‐voltage O redox which is distinct from high‐voltage NB O redox. This π‐type oxygen redox mode expands the fundamental theories of anionic redox and provides a new design route to achieve high‐capacity Li‐rich cathode materials.