Combined NMR and XAS study on local environments and electronic structures of electrochemically Li-ion deintercalated Li1-xCo1/3Ni1/3Mn1/3O2 electrode system

Combined Li-6 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 Li1-xCo1/3Ni1/3Mn1/3O2 cathode material. The Li-6 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. (C) 2004 The Electrochemical Society.