Improved Li6.5La3Zr1.5Nb0.5O12 electrolyte and effects of atmosphere exposure on conductivities

Cubic Li6.5La3Zr1.5Nb0.5O12 ceramic electrolyte is prepared by a simple modified sol-gel process. Quite fine mother powders are obtained through pressing, crushing and grinding for several times instead of ball milling. The Li6.5La3Zr1.5Nb0.5O12 electrolyte achieves a high relative density of similar to 97% and excellent properties with a high ionic conductivity of 7.00 x 10(-4) S cm(-1) and a low electronic conductivity of 9.94 x 10(-8) S cm(-1) at room temperature. When exposed to the atmosphere, the ionic conductivity of Li6.5La3Zr1.5Nb0.5O12 gradually decreases to 2.25 x 10(-4) S cm(-1) after 22 days. EIS test provides a direct evidence to demonstrate an increase trend of grain boundary impedances. Rietveld refinement reveals the lattice parameters increase with the exposure time and obvious changes in lithium occupancies at 24d and 96h sites occur before and after the atmosphere exposure. A linear increase of Li2CO3 impurity with exposure days is also found. Moreover, the electronic conductivity of Li6.5La3Zr1.5Nb0.5O12 is reduced as well after atmosphere exposure (from 9.94 x 10(-8) S cm(-1) to 7.60 x 10(-8) S cm(-1)). This work reports a simple, effective method for the preparation of high-quality LLZO ceramics and may be helpful to further concern on the atmosphere stability of them.

Automated summary

A cubic Li6.5La3Zr1.5Nb0.5O12 ceramic electrolyte with high ionic conductivity and low electronic conductivity is prepared using a modified sol-gel process. However, the ionic conductivity decreases gradually when exposed to the atmosphere. This study provides insights into the atmosphere stability of LLZO ceramics.