Bulk Li mobility enhancement in Spark Plasma Sintered Li(7−3x)AlxLa3Zr2O12 garnet

Abstract : Li (7−3x) Al x La 3 Zr 2 O 12 (LLAZO) Al-doped garnets display high ionic conductivity in the range of ~10-4 S.cm-1 at room temperature and are thus envisioned for future solid-state batteries. In this study, LLAZO powders with two doping levels were synthetized using a solid-state route and sintered using Spark Plasma Sintering (SPS). Both pristine and SPS crushed pellet powders were investigated using X-Ray Diffraction (XRD) confirming the formation of the most conducting cubic phase. Ionic conductivity measurements were performed using electrochemical impedance spectroscopy. Li and Al distributions among available sites were identified using Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) experiments, and Li mobility was explored using 7 Li static wideline NMR spectroscopy. Results show that SPS treatment, beyond producing highly densified pellets, mainly modifies Al distribution and strongly impacts the bulk Li + mobility.