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Scheme illustrating the differences between the established ionic Ni redox model of LNO and the covalent Ni-O redox observed with DMFT calculations (seeFigure 1), which is very close to an O redox model. The standard understanding considers Ni to undergo the greatest changes in oxidation state when a battery is cycled, from +3 in LiNiO2to +4 in NiO2and +2 in the prototype rock salt NiO during degradation. O is commonly considered to be less affected, mostly assuming a charge state of -2. All our DFT and DMFT simulations instead suggest that O undergoes the greatest changes in charge state, from -1.5 in LiNiO2to -1 in NiO2and -2 in NiO. Ni is less affected and remains in a charge state of close to +2.

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