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

Li 1.20 − y Ni 0.17 Co 0.10 Mn 0.53 O 2 ( 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 Li 1.20 Ni 0.17 Co 0.10 Mn 0.53 O 2 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 3 a and 3 b as [Li 0.988 Ni 0.012 ] 3 a [Li 0.212 Ni 0.158 Mn 0.53 Co 0.10 ] 3 b O 2 . The M ( M = Ni, Co, and Mn) K and L-edge XAFS results suggested that the Li de-intercalation from Li 1.20 Ni 0.17 Co 0.10 Mn 0.53 O 2 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 Li 2 CO 3 or Li 2 O 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.