Rapid cooling method for synthesis of high conducting rhombohedral phase stabilized LiZr2(PO4)3 solid electrolyte

Abstract

LiZr2(PO4)3 (LZP) solid electrolyte shows excellent stability with Li metal anode and other electrode materials but suffers due to poor ionic conductivity at ambient temperatures. It synthesizes as a low conducting (10−8 S cm−1) triclinic phase at room temperature (RT), which undergoes a phase transition to a high conducting (10−5 S cm−1) rhombohedral phase at around 60 °C. Partial substitution of Zr4+ in LZP with La3+, Sr3+, Al3+, etc. is found to stabilize this high conducting phase at RT. In this work, rhombohedral phase stabilized LZP samples are prepared via the method of rapid cooling, wherein the samples are sintered at high temperatures for relatively short durations of time followed by rapid cooling/quenching to RT. Sample properties are characterized using XRD, SEM, and impedance spectroscopy (IS) techniques. Pristine LZP which was quenched to RT after sintering for 1200 °C/5h exhibited a high RT ionic conductivity value of 0.9 × 10−5 S cm−1. This high ionic conductivity value for pristine LZP has never been reported before. Pristine LZP is mostly found to possess ionic conductivity value in the range of 10−8–10−7 S cm−1 at RT.