Reversible Anionic Redox Activities in Conventional LiNi1/3Co1/3Mn1/3O2 Cathodes

Redox reactions of oxygen have been considered critical in controlling the electrochemical properties of lithium‐excessive layered‐oxide electrodes. However, conventional electrode materials without overlithiation remain the most practical. Typically, cationic redox reactions are believed to dominate the electrochemical processes in conventional electrodes. Herein, we show unambiguous evidence of reversible anionic redox reactions in LiNi1/3Co1/3Mn1/3O2. The typical involvement of oxygen through hybridization with transition metals is discussed, as well as the intrinsic oxygen redox process at high potentials, which is 75 % reversible during initial cycling and 63 % retained after 10 cycles. Our results clarify the reaction mechanism at high potentials in conventional layered electrodes involving both cationic and anionic reactions and indicate the potential of utilizing reversible oxygen redox reactions in conventional layered oxides for high‐capacity lithium‐ion batteries. At high potentials, with high potential for the use of conventional layered oxides to create high‐capacity batteries, reversible anionic redox activity in LiNi1/3Co1/3Mn1/3O2 was proved experimentally by state‐of‐the‐art characterization techniques. The cationic and anionic redox activities of LiNi1/3Co1/3Mn1/3O2 were quantified by considering transition‐metal–oxygen hybridization separately from intrinsic lattice O redox reactions at high potentials (see picture).