Neutron diffraction studies on structural effect for Ni-doping in LiCo1 − xNixO2

We report structural effect for Ni-doping in lithium cobalt oxide (LiCoO2) studied by the time-of-flight (TOF) neutron powder diffractions measured at RT. Crystal and local structures of LiCo1 − xNixO2 (x = 0, 0.2, 0.4, 0.6, 0.8, 1) powders, that were prepared by the solid-state reaction methods, have been respectively examined by using the IBARAKI Neutron Design Diffractometer (iMATERIA) of JPARC and Nanoscale-Ordered Material Diffractometer (NOMAD) of ORNL. The Rietveld refinement for neutron diffraction data of LiCo1 − xNixO2 that all have been indexed to the rhombohedral system with trigonal symmetry in the space group R-3m, revealed the lattice parameter c/a ratio that tends to the ideal value as decreasing Ni-contents, while the atomic pair distribution function (PDF) analysis for neutron data of LiCo1-xNixO2 revealed that the Co-O and the Ni-O pair correlation lengths under the first peak of G(r) that respectively vary from 1.88 to 1.9 Å and from 1.98 to 2.0 Å, with average Ni-O correlation length (1.99 Å) seems to be slightly larger than average Co-O correlation length (1.89 Å). Rather than that resulted by the Rietveld analysis, the PDF analysis suggested that the diffusion pathways between Co-O in the LiCo1 − xNixO2 system remain stable at ~ 1.89 Å for all Ni-contents.