Oxygen redox in LiNiO2 cathodes

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. 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. Oxygen hole formation controls stability in LiNiO2 cathodesGenreith-Schriever et al.JouleJuly 19, 2023In BriefThe energy density of Li-ion batteries can be increased using high-voltage cathode materials such as Ni-rich layered oxides. These cathodes, however, are known to lose oxygen, causing electrolyte oxidation and battery failure. Our work provides a comprehensive understanding of both bulk and surface oxygen "Ni–O" redox reactions, providing a mechanism for singlet oxygen release in LiNiO2 and highlighting the role of O redox in these processes. The findings provide insights into how to mitigate degradation in future cathode materials. Full-Text PDF Open Access