Low-Temperature Sintering of Garnet-Type Li7La3Zr2O12 Solid Electrolyte with Li3BO3 Additive Prepared by Polymeric Complex Method

Abstract

In this study, a Li₃BO₃ (LBO) compound is synthesized via the heat-treatment of polymeric precursors containing Li and B in air at 700 °C for 5 h to use as a sintering additive for the densification of Li7La₃Zr₂O12 (LLZ) solid electrolyte. The synthesized LBO powder is suitable for promoting the densification, cubic phase stability, and ionic conductivity of LLZ. X-ray diffraction analysis indicated that monophasic cubic LLZ could be obtained by the addition of LBO in sintering, changing to cubic LLZ phase from LZ impurities detected in raw LLZ. The sintered LLZ-12 wt% LBO showed that the densification of the LLZ with LBO occurred by a coupling effect including the particle rearrangement of LLZ in the melted LBO phase and grain growth of LLZ particles. The density of the LLZ-12 wt% LBO composite sintered at 1100 °C for 8 h was 3.72 g/cm³ (86% of theoretical density); the composite showed the high Li-ion conductivity of 1.18×10-4 S·cm-1 at 28 °C.