In situ Raman spectroscopy of layered solid solution Li2MnO3-LiMO2 (M = Ni, Mn, Co)

Lithium rich manganese oxide based materials are emerging as possible high energy density cathode materials for lithium ion batteries. In the present research, we have investigated the first charge/discharge profile behavior of Li1.2Ni0.175Co0.1Mn0.52O2 via in situ Raman spectroscopy. X-ray diffraction studies confirm the presence of cation ordering in the transition metal layers. Scanning electron microscopy shows the homogeneous distribution of highly dense spherical agglomerates of similar to 5 mu m size. Steady decrease in impedance up to similar to 4.5 V followed by a less steep increase as the cell voltage traversed the first charge cycle has been confirmed by electrochemical impedance spectroscopy. Raman spectroscopy shows that the extraction of lithium takes place from both the transition metal layers as well as lithium layers in the voltage range of 4.1-4.4 V. The oxygen removal becomes severe in the voltage range of 4.55-4.6 V, after which the diffusion of the transition metal ions to the vacant sites takes place. (C) 2012 Elsevier B.V. All rights reserved.