Combined NMR and XAS Study on Local Environments and Electronic Structures of Electrochemically Li-Ion Deintercalated Li[sub 1−x]Co[sub 1/3]Ni[sub 1/3]Mn[sub 1/3]O[sub 2] Electrode System

Abstract

Combined 6 Li 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 - x Co 1 / 3 Ni 1 / 3 Mn 1 / 3 O 2 cathode material. The 6 Li MAS NMR results showed the presence of Li in the Ni 2 + /Mn 4 + 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 Ni 2 + ions, while manganese ions remain mostly unchanged in the Mn 4 + 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.