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 O2 formation mechanism was elucidated. This work provides an opportunity to reassess the current understanding of conventional cathode materials.