Metal‐Ligand π Interactions in Lithium‐Rich Li2RhO3 Cathode Material Activate Bimodal Anionic Redox. Issue 30 (19th June 2021)

• Record Type: Journal Article
• Authors: Zhang, Kun; Jiang, Zewen; Ning, Fanghua; Li, Biao; Shang, Huaifang; Song, Jin; Zuo, Yuxuan; Yang, Tonghuan; Feng, Guang; Ai, Xinping; Xia, Dingguo
• Is Part Of: Advanced energy materials. Volume 11:Issue 30(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-06-19
• Subjects: π interaction -- anionic redox -- metal‐ligand Interactions -- Li‐ion batteries; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.202100892
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract: 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 Li2 RhO3 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. Abstract : π‐type hybridizations in Li‐rich oxide (LROs) stemming from orbital overlap between transition metal (TM) and O 2p states are investigated. In Li2 RhO3, O preferentially occupies the hybridized π* states, leading a novel π‐type redox at low voltages that is accompanied by non‐bonding oxygen redox at high voltages, indicating that bimodal O redox can occur in LROs depending on the characteristics of the TM and anions.