Structural and electrical studies of olivine LiNi1 − x(Co0.5Mn0.5)xPO4 (0 ≤ x ≤ 1) at high temperature

A series of olivine-structured of LiNi1 − x(Co0.5Mn0.5)xPO4 (0 ≤ x ≤ 1) compositions have been synthesized by two-step conventional solid-state method at high temperature of 1000 °C followed by slow cooling or quenching. The XRD patterns of the obtained samples confirmed the formation of LiNi1 − x(Co0.5Mn0.5)xPO4 (0 ≤ x ≤ 1) phase with orthorhombic structure, Pmna space group. The lattice parameters determined by Rietveld refinements increase significantly as Co and Mn substitute for Ni. The SEM images show that the sample x = 0.8 started to partially melt while x = 1 has fully melted at temperature 1000 °C. The AC impedance spectroscopy measurements have revealed that the conductivity measured at 300 °C of all the slow-cooled samples can be enhanced by quenching. The quenched sample with x = 0.8 showed the largest increment of conductivities from 3.70 × 10−8 S cm−1 to 1.05 × 10−6 S cm−1 as a function of the cooling condition.