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

Li 6.5 La 3 Zr 1.5 Nb 0.5 O 12 (LLZN) garnet-type structure was synthesized at low temperature with B 2 O 3 addition by solid state reaction method. The effects of B 2 O 3 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 B 2 O 3 content, reaching the maximum value of 92.4% and 1.86×10 −4   S   cm −1 respectively in the sample with 1.4   wt% B 2 O 3 . By contrast, the activation energy reached a minimum value of ~31.5   kJ   mol −1 .