Effects of B2O3 on microstructure and ionic conductivity of Li6.5La3Zr1.5Nb0.5O12 solid electrolyte

Li6.5La3Zr1.5Nb0.5O12 (LLZN) garnet-type structure was synthesized at low temperature with B2O3 addition by solid state reaction method. The effects of B2O3 content on the formation, microstructure, ionic conductivity and activation energy of the LLZN solid electrolytes have been investigated by X-Ray diffraction (XRD), scanning electron microscopy (SEM) and alternate current (AC) impedance spectroscopy. The cubic LLZN phase was obtained after calcining at 850 °C for 6 h and no phase evolution was observed after sintering at 1100 °C for 6 h. The relative density and lithium ion conductivity increased first and then decreased with increasing B2O3 content, reaching the maximum value of 92.4% and 1.86×10−4 S cm−1 respectively in the sample with 1.4 wt% B2O3. By contrast, the activation energy reached a minimum value of ~31.5 kJ mol−1.