Rhombohedral Li1+xYxZr2-x(PO4)3 Solid Electrolyte Prepared by Hot-Pressing for All-Solid-State Li-Metal Batteries

NASICON-type solid electrolytes with excellent stability in moisture are promising in all-solid-state batteries and redox flow batteries. However, NASIOCN LiZr2(PO4)(3) (LZP), which is more stable with lithium metal than the commercial Li1.3Al0.3Ti1.7(PO4)(3), exhibits a low Li-ion conductivity of 10(-6) S cm(-1) because the fast conducting rhombohedral phase only exists above 50 degrees C. In this paper, the high-ionic conductive rhombohedral phase is stabilized by Y3+ doping at room temperature, and the hot-pressing technique is employed to further improve the density of the pellet. The dense Li1.1Y0.1Zr1.9(PO4)(3) pellet prepared by hot-pressing shows a high Li-ion conductivity of 9 x 10(-5) S cm(-1), which is two orders of magnitude higher than that of LiZr2(PO4)(3). The in-situ formed Li3P layer on the surface of Li1.1Y0.1Zr1.9(PO4)(3) after contact with the lithium metal increases the wettability of the pellet by the metallic lithium anode. Moreover, the Li1.1Y0.1Zr1.9(PO4)(3) pellet shows a relatively small interfacial resistance in symmetric Li/Li and all-solid-state Li-metal cells, providing these cells a small overpotential and a long cycling life.