High-Throughput Studies of Li-La-Zr-O Garnet Solid Electrolytes

Abstract

Development of next-generation lithium-ion batteries has increasingly focused on all-solid batteries employing either ceramic, polymer, or glass electrolytes in order to address shortcomings in currently commercialized liquid electrolyte lithium-ion batteries including safety, limited lifetime and lower energy densities resulting from the instability with respect to Li metal anodes.[1] Lithium lanthanum zirconium oxide (LLZO) is a leading candidate for solid Li-batteries due to its high lithium-ion conductivity, stability in air and with Li metal, and compatibility with high-voltage cathodes.[2],[3],[4] Despite significant progress being made in its development, our understanding of LLZO is limited by the relatively small number of compositions which have been studied; especially considering the leading contender is a pseudo-quaternary oxide (Ga-doped LLZO).[5] Herein, we have applied a high-throughput methodology for synthesizing, characterizing, and testing sets of 64 LLZO electrolytes at the mg-scale. This has allowed the study of the entire Li-La-Zr-O pseudo-ternary system by enabling a single researcher to explore hundreds of compositions in a single week. We employ a sol-gel synthesis method whereby a robot dispenses reagent solutions in order to vary the composition across a well-plate. After drying the samples and burning off the citrates, the resulting powders are pressed into pellets using a custom-made 64-pellet die and the pellets are sintered at the desired temperature. The high-throughput characterization techniques utilized include powder X-ray diffraction, electrochemical impedance spectrometry and electrochemical cycling in order to test electrolyte stability; with each method performed on 64 samples simultaneously.The resulting structural phase diagrams will be presented for various sintering temperatures along with the extracted electrochemical properties. Given that ionic conductivity in ceramic electrolytes depends heavily on the presence/absence of certain structural defects, the complete understanding of the phase diagrams will significantly accelerate the development of this important class of advanced materials. [1] D. Aurbach et al., Electrochimica Acta 2004, 50, 247-254. [2] F. Zheng, et al., J. Power Sources 2018, 389, 198-213. [3] Q. Liu, et al., J. Power Sources 2018, 389, 120-134. [4] T. Thompson, et al., ACS Energy Letters 2017, 2, 462-468. [5] J-F. Wu, et al., ACS Applied Mater Interfaces 2017, 9, 1542-1552