High-pressure synthesis of solid solutions between trigonal LiNiO2 and monoclinic Li[Li1/3Ni2/3]O2

High-pressure synthesis in an oxygen-rich atmosphere yields solid solutions between LiNiO₂ and Li₂NiO₃ over the whole concentration range. Structural characterization of the high-pressure oxides was performed using powder XRD, SEM analysis, IR spectroscopy, EPR spectroscopy at 9.23 and 115 GHz and magnetic susceptibility measurements. The crystal structure of Li[Li_xNi_1−x]O₂ ,, changes from trigonal R-3m to monoclinic C2/m at Li-to-Ni ratio of 2 (or ). The incorporation of Li into NiO₂-layers causes a decrease in the mean Li-O and Ni_1-xLi_x-O bond distance. Li and Ni ions in the mixed Ni_1-xLi_xO₂-layers display a tendency to order at a short length scale in such a way that mimics the Li_1/3Ni_2/3-arrangment of the end Li[Li_1/3Ni_2/3]O₂ composition. The charge distribution in these oxides proceeds via Ni³⁺ and Ni⁴⁺ ions.