Combined NMR and XAS Study on Local Environments and Electronic Structures of Electrochemically Li-Ion Deintercalated Li_1-xCo _1/3Ni_1/3Mn_1/3O₂ Electrode System

Combined ⁶Li magic-angle spinning (MAS) NMR, in situ metal K-edge (hard) X-ray absorption spectroscopy (XAS), and O K-edge (soft) XAS have been carried out during the first charging process for layered Li _1-xCo_1/3Ni_1/3Mn_1/3O₂ cathode material. The ⁶Li MAS NMR results showed the presence of Li in the Ni²⁺/Mn⁴⁺ layers, in addition to the expected sites for Li in the lithium layers. On charging, Li ions in both the transition metals and lithium layers are removed and no new resonances are observed. The metal K-edge XAS results suggest that the major charge compensation at the metal site during charge is achieved by oxidation of Ni²⁺ ions, while manganese ions remain mostly unchanged in the Mn⁴⁺ state. From observation of O K-edge XAS results, one can conclude that a large, portion of the charge compensation during charge is achieved in the oxygen site. This work provides the possibility of larger capacity of the electrode material using Li in the transition metal layers and contribution of oxygen during charge.