Effect of SnO-P2O5-MgO glass addition on the ionic conductivity of Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte

NASICON-type structured compounds Li1+xMxTi2-x(PO4)(3) (M = Al, Fe, Y, etc.) have captured much attention due to their air stability, wide electrochemical window and high lithium ion conductivity. Especially, Li1.3Al0.3-Ti-1.7(PO4)(3) (LATP) is a potential solid electrolyte due to its high ionic conductivity. However, its actual density usually has a certain gap with the theoretical density, leading the poor ionic conductivity of LATP. Herein, LATP solid electrolyte with series of SnO-P2O5-MgO (SPM, 0.4 wt%, 0.7 wt%, 1.0 wt%, 1.3 wt%) glass addition was successfully synthesized to improve the density and ionic conductivity. The SPM addition change Al/Ti-O bond and P-O bond distances, leading to gradual shrinkage of octahedral AlO6 and tetrahedral PO4. The bulk conductivity of the samples increases gradually with SPM glass addition from 0.4 wt% to 1.3 wt%. Both SPM and the second-phase LiTiPO5, caused by glass addition, are conducive to the improvement of compactness. The relative density of LATP samples increases first from 0 wt% to 0.7 wt%, and then decreases from 0.7 wt% to 1.3 wt% with SPM glass addition. The grain boundary conductivity also changes accordingly. Especially, the highest ionic conductivity of 2.45 x 10(-4) S cm(-1), and a relative density of 96.72% with a low activation energy of 0.34 eV is obtained in LATP with 0.7 wt% SPM. Increasing the density of LATP solid electrolyte is crucial to improve the ionic conductivity of electrolytes and SPM glass addition can promote the development of dense oxide ceramic electrolytes.

Automated summary

NASICON-type structured compounds Li1+xMxTi2-x(PO4)(3) have attracted attention for their stability and high lithium ion conductivity. This study successfully synthesized LATP solid electrolyte with SnO-P2O5-MgO glass addition to improve density and ionic conductivity. Different concentrations of SPM glass addition altered Al/Ti-O and P-O bond distances, affecting the relative density and bulk conductivity of LATP samples.