Oxygen redox in LiNiO2 cathodes

Abstract

Assigning oxidation states and understanding the oxygen redox mechanism is crucial for designing superior cathode materials in lithium-ion batteries. The working mechanism of stoichiometric LiNiO2 has been regarded as Ni-dominant redox with partial O contribution through covalent Ni-O bonding for several decades. However, in this issue of Joule, Morris, Grey, and co-workers reported that Ni rarely participates in the redox reaction, and oxygen primarily acts as the redox center through a combination of experimental analysis and computational prediction. Also, the highly reactive singlet O-2 formation mechanism was elucidated. This work provides an opportunity to reassess the current understanding of conventional cathode materials.