Synthesis of Ta-doped Li7La3Zr2O12 for application in solid-state electrolyte

Abstract

Solid-state batteries have emerged as a major focus in rechargeable battery research. Among them, cubic-phase of lithium lanthanum zirconium oxide (LLZO) demonstrates excellent room-temperature ionic conductivity, low activation energy, and high thermal stability against lithium metal. Conventional LLZO synthesis struggles with particle size control and large-scale uniform production, limiting commercial applications. Thus, developing an efficient synthesis route for high-quality LLZO is critical. In this work, a refined standard operating procedure (SOP) for fabricating dense pellets from powder was established using commercial powder. Systematic optimization of green body properties and sintering yielded ceramics with 95.8% relative density, 0.49 mS cm⁻¹ conductivity at 20 °C and 0.25 eV activation energy (20–40 °C). Furthermore, the study introduces a spray-drying synthesis approach for cubic-phase Ta-doped LLZO powder. Compared to commercial powders, the synthesized LLZTO produced similarly dense pellets (up to 96.4%) with comparable electrochemical performance. The best sample reached an ionic conductivity of 0.36 mS cm⁻¹ at 20 °C and 0.52 mS cm⁻¹ at 40 °C, with a minimum activation energy of 0.23 eV. Preliminary tests integrated synthesized LLZTO into 3D printing inks. After de binding and sintering, phase stability or crystallite size were unaffected, but mechanical fragility prevented reliable electrochemical testing. Overall, this study demonstrates both an effective spray drying route for scalable LLZTO synthesis and the feasibility of fabricating oxide-based solid electrolytes via 3D printing. Further optimization is needed to improve the mechanical strength and reproducibility of printed structures before achieving consistent electrochemical characterization.