Cr and V substituted LiSn2P3O12 solid electrolyte materials

Li1+xCrxSn2−xP3−yVyO12 solid electrolyte materials with x = 0.8 and y = 0, 0.2, 0.4, 0.6 and 0.8 are prepared by mechanochemical milling method followed by heat treatment at 1000 °C. The conductivities of the pellets are determined using AC impedance spectroscopy. X-ray diffraction is used to determine the crystallographic phases while scanning electron microscope and energy dispersive X-ray are used to study morphological properties and elemental compositions respectively. Combined substitution of both chromium and vanadium in LiSn2P3O12 system results in enhancement of room temperature ionic conductivity up to two orders of magnitude compared to the unsubstituted LiSn2P3O12 system. The increase in conductivity in the systems with y of 0.2 and 0.4 as compared to the sample of y = 0 is attributed to the absence of Li6P6O18 impurities. Furthermore, the sample with y = 0.4 shows higher ionic conductivity compared to the sample with y = 0.2. This sample exhibits bulk conductivity of 10−3 S cm−1 and grain boundary conductivity of 10−5 S cm−1 at elevated temperatures. This is attributed to larger crystallite size and better contact between grains. This sample is also structurally stable toward temperature and thus suitable for thermal electrochemical device application. ► Li1.8Cr0.8Sn1.8P3−yVyO12 pellets were obtained without using any binding agent. ► V substitution enhances bulk conductivity of LiSn2P3O12 by two orders of magnitude. ► V substitution increases grain boundary conductivity by one order of magnitude. ► Conductivities changes are attributed to structural changes due to V substitution.