Operando X-ray Raman Ni 2p spectra of LiNi_xMn_yCo1-x-yO₂ lithium-ion battery electrodes

Lithium manganese nickel oxides are a prominent class of materials used for positively charged lithium-ion batteries. Three different archetype stoichiometries of lithium nickel manganese cobalt oxides (NMC) were studied with bulk-sensitive X-ray Raman and surface-sensitive soft X-ray absorption spectroscopy. We have conducted complementary operando battery X-ray experiments on the NMC622 electrode over one full charge and discharge cycle in a specifically designed operando battery cell. The ex situ NEXAFS spectra of the Ni L-edges show distinct differences in their multiplet characteristics depending on the cathode composition. The obtained operando X-ray Raman spectra show changes in the branching ratio of the Ni 2p spectra and confirms that the state of charge of the battery correlates with changes in the bulk of the electrode.