A shortcut to garnet-type fast Li-ion conductors for all-solid state batteries

By Afyon, Semih; Kr
Published in J. Mater. Chem. A The Royal Society of Chemistry 2015

Abstract

Ga-doped Li?La?Zr?O?? garnet structures are among the most promising electrolytes for all-solid state Li-ion-batteries. The synthesis and processing of garnet-type fast Li-ion conductors depend on conventional sol-gel and solid state syntheses and sintering that are usually done at temperatures above 1050 [degree]C to reach the high Li-ion conducting cubic phase. This process results in micron-sized particles and potential Li-loss, which are unfavorable for further processing and electrode-electrolyte assembly. Here, we tackle this problem and report a novel low temperature synthesis-processing route to stabilize the cubic phase of Li?La?Zr?O??, while keeping the nanocrystallites at [similar]200-300 nm. Li?La?Zr?O?? phases are obtained at temperatures as low as 600 [degree]C by a modified sol-gel combustion method utilizing mainly nitrate precursors, and the sintering temperature is lowered by [similar]200 [degree]C compared to the state-of-art. Through a new model experiment, we also shed light on the conditions influencing the tetragonal to cubic phase transformation via homogeneous Ga-diffusion and incorporation occurring at a surprisingly low temperature of [similar]100 [degree]C for a post-annealing step. The sintered pellets of the newly obtained Li6.4Ga0.2La?Zr?O?? deliver high bulk Li-ion conductivities in the range of [similar]4.0 [times] 10-4 S cm-1 at 20 [degree]C, and a wide thermal operation window is accessible through its characteristic activation energy of [similar]0.32 eV. We report that there is an optim

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