Study on Li de-intercalation/intercalation mechanism for a high capacity layered Li1.20Ni0.17Co0.10Mn0.53O2 material

Li1.20-yNi0.17Co0.10Mn0.53O2 (y = 0.1-0.93) were prepared electrochemically and characterized using synchrotron XRD and XAFS measurements. Structural analysis using XRD data demonstrated that the lattice parameters of Li1.20Ni0.17Co0.10Mn0.53O2 are a = 0.285214(7) nm and c = 1.42173(3) nm and that the chemical composition can be expressed referring to the Wyckoff positions 3a and 3b as Li0.988Ni0.012](3a)[Li0.212Ni0.158Mn0.53Co0.10](3b)O-2.. The M (M = Ni, Co, and Mn) K and L-edge XAFS results suggested that the Li de-intercalation from Li1.20Ni0.17Co0.10Mn0.53O2 proceeded mainly by the oxidation of Ni and Co ions up to y = 0.4 and then by the removal from oxygen from the lattice up to y = 0.93. On the other hand, the O K-edge XANES results indicated no increase in Li2CO3 or Li2O on the surface of the positive electrode materials with Li de-intercalation. These results demonstrate that the XAFS method using a combination of soft and hard X-ray is effective way of clarifying the Li de-intercalation/intercalation of the positive electrode materials. (C) 2012 Elsevier B.V. All rights reserved.