La2O3 optimized the structure and ionic conductivity of 0.75Li2O-0.125B2O3-0.125SiO2 ceramic solid electrolyte sintering additives

The use of sintering additives with low melting point, high ionic conductivity, and high wettability can reduce the grain boundary impedance of the ceramic electrolyte. As a commonly used sintering auxiliary for inorganic ceramic electrolytes, Li2O-B2O3-SiO2 has a role in reducing the sintering temperature of ceramic electrolyte and improving sintering density and ionic conductivity. The low ionic conductivity affects its breadth of applications. Improving its performance is conducive to adjusting the grain boundary impedance of ceramic electrolytes. In this work, the (0.75-3x) Li2O-0.125B2O3-0.125SiO2-xLa2O3 ceramic solid electrolyte sintering additives prepared by ultra-fast melting method are mainly studied, and the effects of different amounts of La2O3 doping on their structure and ionic conductivity are explored. La2O3 doping modulates the electrolyte structure by influencing [BO3]3- and [BO4]5- content, Si-O recombination. And reduce the binding force of groups to lithium ions in the system, increase its ionic conductivity, and reduce the activation energy. At x = 0.02, the room temperature ionic conductivity of 0.69Li2O-0.125B2O3-0.125SiO2-0.02La2O3 is 4.70×10-6 S/cm-1, and the activation energy is 0.30 eV, which is a higher improvement than that of undoped. Experiments show that it reduces the grain boundary impedance of LiTa2PO8 and improves the room temperature ionic conductivity and density.