Insertion of binary LiCl-P2O5 glass between Li+ NASICON crystallites and its effect on controlling inter-grain transport

Abstract

Li+ ion conducting glass-ceramic composites have been prepared from fine flakes of ion conducting binary oxide glass i.e. 2LiCl-P2O5 (LCPO) and nanograins of LiTi2(PO4)3 (LTP) using milling assisted synthesis route. The effect of variation of glass content and composition in the composite has been systematically investigated. Milling and heat treatment during glass-ceramic formation do not lead to any decomposition or formation of a new phase. As suggested by XRD, DSC and conductivity-temperature cycles, LCPO remains in glassy state in the composite. The tiny glassy flakes are seen to be homogenously embedded in between the LTP crystallites as confirmed by FESEM. The bulk (σbulk) and grain boundary (σGB) conductivity values have been found to be ~4 × 10−5 Ω−1 cm−1 and ~8 × 10−6 Ω−1 cm−1 at 100 °C for the glass-ceramic with 20(60LCPO)-80(LTP-18h) which are significantly higher than those of pristine LTP pellets prepared under similar sintering conditions. Ionic mobility measurements suggest that mobile Li+ ion concentration existing in glassy phase at the grain boundaries contribute significantly to inter grain transport. These glass-ceramics have been found to be thermally stable up to a temperature of ~300 °C. Cyclic voltammetry measurements obtained at 100 °C suggest good stability under different electrode configurations.