An innovative synthesis: Garnet lithium-ion conductive solid-state electrolyte synthesized by an arc melting process
PRADEILLES S. 2,3, NONNET E. 3, GABAUDAN V. 3, SIMON P. 2, TABERNA P. 2, ROZIER P. 2
1 CIRIMAT / Saint-Gobain, Toulouse, France; 2 CIRIMAT, Toulouse, France; 3 Saint-Gobain Research Provence, Cavaillon, France
All-solid-state batteries (ASSB) have drawn a real scientific interest in the last decade, guided by new electrolyte ceramic materials discovery. Among them, Li6,6La3Zr1,6Ta0,4O12, a garnet?type electrolyte (LLZO:Ta) shows close to equal ionic conductivity compared to conventional liquid ones [1]. Its high mechanical properties guaranty use of lithium metal at the anode, allowing an important gain in terms of energy density [2, 3]. However, though (electro?)chemical stable vs. lithium metal, LLZO:Ta suffers from air sensitivity [4] and requires many synthesis steps with parameters drastically affecting the properties of the as obtained material [5] as well as the shaping procedure.
In this report we propose a new, efficient, fast and one?step synthesis of LLZO:Ta by direct moulding of the fused raw materials, using arc melting process. We will show that this process allows getting in one?step dense cubic LLZO:Ta (relative density above 95%) with ionic conductivity determined using Electrochemical Impedance Spectroscopy close to bulk properties of LLZO:Ta showing the perfect mastering of grain boundaries. These properties are maintained even for samples stored in ambient air using a simple anhydrous polishing of the part indicating that only the surface is protonated thanks to high density.
Moreover, we will present operando XRD characterization of LLZO:Ta/ NMC 811 powder mixture which shows high thermal and chemical stability of the catholyte mixture in a wide range of temperature. We will also show that the powder was used to successfully prepare, using Spark Plasma Sintering technique, both electrolyte separator membranes with relative density above 98% and positive electrode composites NMC 811/LLZO:Ta (70/30 vol%).
This report will allow concluding that the as prepared LLZO:Ta is perfectly adapted to be used as ionic conductor in the different components of Li-ASSB while the remaining issue lies in the limited thermal chemical stability of the active material itself.
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