Insights into the sinterability and electrical properties of Li1.3Al0.3Ti1.7(PO4)3-(Li2CO3·Bi2O3) composite electrolytes

The NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP) is considered to be one of the most promising solid electrolytes because of its excellent chemical stability against moisture and considerable total ionic conductivity. Nevertheless, the poor sinterability and low grain boundary ionic conductivity of LATP limit its practical commercial applications. Herein, Li2CO3·Bi2O3 (abbreviated as LB), as a sintering aid, was introduced into LATP to improve its sinterability and ionic conductivity. It was demonstrated that the addition of LB promoted the liquid phase sintering of LATP by forming the secondary phases with a low melting point, thereby promoting the growth of grains and making the contact between the grains closer. With the help of LB, the sintering temperature of LATP was reduced to about 900 °C. A series of comparative investigations indicated that the LATP-2LB ceramic pellets sintered at 900 °C exhibited the highest total ionic conductivity of 0.673 mS/cm. Meanwhile, the relative density and grain boundary ionic conductivity of LATP-2LB ceramic pellets sintered at 900 °C reached 95.28% and 3.835 mS/cm, respectively, which is much higher than 77.16% and 0.264 mS/cm of LATP-0LB ceramic pellets sintered at the same temperature. Obviously, LB can effectively improve the sinterability of LATP while increasing its ionic conductivity, providing a new strategy for preparing LATP ceramics with excellent properties.