High lithium ion conductive Li7La3Zr2O12 by inclusion of both Al and Si

High lithium-ion (Li+) conductive garnet-structured lanthanum lithium zirconate (LLZ) solid electrolyte is prepared by incorporation of appropriate amounts of silicon (Si) and aluminum (Al). The resultant pelletized LLZ obtains total Li+ conductivity of 6.8 x 10(-4) S cm(-1) at 298 K. This improved conductivity is nearly identical with the bulk Li+ conductivity of the LLZ reported earlier, suggesting that the grain boundary resistance is effectively reduced by the incorporation of Si and Al. Microanalyses by transmission electron microscopy coupled with energy-dispersive X-ray microanalysis and electron energy-loss spectroscopy revealed the presence of amorphous Li-Al-Si-O with nano crystalline LiAlSiO4 at grain boundaries. Fast lithium-ion transport around the amorphous Li-Al-Si-O/LiAlSiO4 interface will facilitate Li+ transport between the LLZ particles, resulting in the improvement of the total Li+ conductivity of LLZ. (C) 2011 Elsevier B.V. All rights reserved.