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Anionic Redox Activity Regulated by Transition Metal in Lithium‐Rich Layered Oxides
Author(s) -
Song JunHyuk,
Yoon Gabin,
Kim Byunghoon,
Eum Donggun,
Park Hyeokjun,
Kim DoHoon,
Kang Kisuk
Publication year - 2020
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.202001207
Subject(s) - redox , lithium (medication) , cationic polymerization , transition metal , materials science , oxygen , inorganic chemistry , electrochemistry , metal , oxidation state , chemistry , catalysis , polymer chemistry , organic chemistry , electrode , medicine , metallurgy , endocrinology
The anionic redox activity in lithium‐rich layered oxides has the potential to boost the energy density of lithium‐ion batteries. Although it is widely accepted that the anionic redox activity stems from the orphaned oxygen energy level, its regulation and structural stabilization, which are essential for practical employment, remain still elusive, requiring an improved fundamental understanding. Herein, the oxygen redox activity for a wide range of 3 d transition‐metal‐based Li 2 TMO 3 compounds is investigated and the intrinsic competition between the cationic and anionic redox reaction is unveiled. It is demonstrated that the energy level of the orphaned oxygen state (and, correspondingly, the activity) is delicately governed by the type and number of neighboring transition metals owing to the π‐type interactions between LiOLi and M t 2g states. Based on these findings, a simple model that can be used to estimate the anionic redox activity of various lithium‐rich layered oxides is proposed. The model explains the recently reported significantly different oxygen redox voltages or inactivity in lithium‐rich materials despite the commonly observed LiOLi states with presumably unhybridized character. The discovery of hidden factors that rule the anionic redox in lithium‐rich cathode materials will aid in enabling controlled cumulative cationic and anionic redox reactions.