Lithium-nickel cobalt oxides with spinel structure prepared at low temperature. XRD, XPS, and EIS measurements

Li, Co and Ni mixed oxides of composition LiNixCo2 − xO4 (x = 0.25, 0.5, 0.75 and 1) were prepared at 280 °C by the Pechini sol–gel method. The Rietveld refinement of the X-ray diffraction data indicated that all the obtained compounds crystallize in the Fd3m space group characteristic of cubic spinel-related oxides. XPS studies on these oxides reveal the presence of Ni2 +, Ni3 +, Co3 + and Co4 + ions at the surface. The diffusion coefficients of the Li+ ion in the oxide lattice, determined by EIS measurements, are larger (10− 13 cm2s− 1 ≤ D ≤ 10− 10 cm2s− 1) than that shown by the non-substituted cobalt-lithium oxide, LiCo2O4 (D = 10− 16 cm2 s− 1) and present similar values to those of layered oxides of related composition.

► LiNixCo2 − xO4 spinel oxides are prepared by a sol-gel method. ► XPS measurements show Ni2 +, Ni3 +, Co3 + and Co4 + ions. ► Co4+ ions content in the B-spinel sites determinate high charge transference impedance values. ► Low Li+ ion diffusion coefficients on the oxides were observed.