Direct evidence of metal–ligand redox processes in positive electrodes during lithium-based battery operation

TY - JOUR

T1 - Direct evidence of metal–ligand redox processes in positive electrodes during lithium-based battery operation

AU - Páez Fajardo, Galo J

AU - Dogaru, Daniela E

AU - Banerjee, Hrishit

AU - Ans, Muhammad

AU - Ogley, Matthew J W

AU - Majherova, Veronika

AU - Bree, Gerard

AU - McClelland, Innes

AU - Hayashida, Shohei

AU - Puphal, Pascal

AU - Isobe, Masahiko

AU - Keimer, Bernhard

AU - Thakur, Pardeep K.

AU - Lee, Tien Lin

AU - Grinter, Dave C.

AU - Ferrer, Pilar

AU - Cussen, Serena A.

AU - Hepting, Matthias

AU - Piper, Louis F J

N1 - Publisher Copyright: © The Author(s) 2026.

PY - 2026/6/9

Y1 - 2026/6/9

N2 - Describing lithium-based battery positive electrodes based on different transition metal or oxygen-redox regimes can cause confusion in understanding metal–ligand hybridization, oxygen dimerization and degradation processes. Therefore, it is urgent to investigate the electronic structure of these materials and identify the role each cation and anion has in charge compensation at the subnanoscale. Here, using X-ray resonance photoemission spectroscopy, single-impurity Anderson models, spectral simulations and theoretical calculations, we examine redox mechanisms in positive electrodes during lithium-based battery operation. This approach reconciles the redox description of two positive electrode active materials—LiMn0.6Fe0.4PO4 and LiNiO2—in terms of varying degrees of charge transfer using the Zaanen–Sawatzky–Allen framework. In LiMn0.6Fe0.4PO4, the lack of strong hybridization indicates that the capacity results from the depopulation of metal 3d states, that is, conventional metal redox. However, in cells with LiNiO2-based positive electrodes, negative charge transfer dominates, and redox occurs through the formation and elimination of ligand-hole states. These results clarify the role of oxygen in Ni-rich systems and provide a framework to explain how the charge/discharge capacities are linked to oxygen-dominated states in highly covalent systems, without the need to consider oxygen dimerization.

AB - Describing lithium-based battery positive electrodes based on different transition metal or oxygen-redox regimes can cause confusion in understanding metal–ligand hybridization, oxygen dimerization and degradation processes. Therefore, it is urgent to investigate the electronic structure of these materials and identify the role each cation and anion has in charge compensation at the subnanoscale. Here, using X-ray resonance photoemission spectroscopy, single-impurity Anderson models, spectral simulations and theoretical calculations, we examine redox mechanisms in positive electrodes during lithium-based battery operation. This approach reconciles the redox description of two positive electrode active materials—LiMn0.6Fe0.4PO4 and LiNiO2—in terms of varying degrees of charge transfer using the Zaanen–Sawatzky–Allen framework. In LiMn0.6Fe0.4PO4, the lack of strong hybridization indicates that the capacity results from the depopulation of metal 3d states, that is, conventional metal redox. However, in cells with LiNiO2-based positive electrodes, negative charge transfer dominates, and redox occurs through the formation and elimination of ligand-hole states. These results clarify the role of oxygen in Ni-rich systems and provide a framework to explain how the charge/discharge capacities are linked to oxygen-dominated states in highly covalent systems, without the need to consider oxygen dimerization.

UR - https://www.scopus.com/pages/publications/105041446224

U2 - 10.1038/s41565-026-02189-y

DO - 10.1038/s41565-026-02189-y

M3 - Article

C2 - 42265354

AN - SCOPUS:105041446224

SN - 1748-3387

JO - Nature Nanotechnology

JF - Nature Nanotechnology

ER -