Ta-Doped Li7La3Zr2O12 for Water-Stable Lithium Electrode of Lithium-Air Batteries

Garnet-type high lithium ion conductivity solid electrolytes with nominal compositions of Li7-xLa3Zr2-xTaxO12 (x = 0-0.7) were prepared by using a sol-gel precursor and are proposed as the protective layer for a water-stable lithium electrode for lithium-air rechargeable batteries. The Li6.75La3Zr1.75Ta0.25O12 (LLZ-0.25Ta) composition sintered at 1,180 degrees C for 36 h showed the highest relative density of 96.7% and resistance to water permeation. The LLZ-0.25Ta was stable in contacting with lithium metal and also in a saturated LiOH/10 M LiCl aqueous solution. The total and bulk conductivities of the sintered LLZ-0.25Ta pellet were 5.20 x 10(-4) and 6.55 x 10(-4) S cm(-1) at 25 degrees C, respectively. The Li/LLZ-0.25Ta/Li cell showed a stable cell resistance of 310 Omega cm(2) at 25 degrees C for 4 months. However, polarization experiments on the Li/LLZ-0.25Ta/Li cell suggest a lithium dendrite short-circuit after 100 s at 0.5 mA cm(-2) and after 2000 s of polarization at 0.1 mA cm(-2), at room temperature. (C) 2014 The Electrochemical Society. All rights reserved.