Enhanced grain boundary ionic conductivity of LiTa2PO8 solid electrolyte by 75Li2O-12.5B2O3-12.5SiO2 sintering additive

LiTa2PO8(LTPO) has low electrolyte density and many pores at grain boundaries, and it is easy to precipitate dielectric phase LiTa3O8 at grain boundaries. The performance can be improved by adding 75Li2O-12.5B2O3- 12.5SiO2 (LBS) sintering additive with low melting point during sintering. The effects of LBS addition on the microstructure and grain boundary ionic conductivity of LTPO electrolytes were studied. The results showed that the addition of LBS sintering additives reduced the sintering temperature, improved the density and stability of LTPO electrolyte samples, effectively inhibited the precipitation of LiTa3O8 phase, reduced the grain boundary impedance of samples, and improved the total ionic conductivity of electrolytes. When LBS was added at 0.4 wt %, the relative density of LTPO reached 93.54%, the grain boundary impedance decreased from 1243 omega to 248.2 omega, the total ionic conductivity increased from 1.55 x 10-4 S cm-1 to 6.51 x 10-4 S cm-1, and the ionic activation energy was 0.137 eV.