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 10−6S cm−1because the fast conducting rhombohedral phase only exists above 50 °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)3pellet prepared by hot-pressing shows a high Li-ion conductivity of 9 × 10−5S 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)3after contact with the lithium metal increases the wettability of the pellet by the metallic lithium anode. Moreover, the Li1.1Y0.1Zr1.9(PO4)3pellet 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.Keywords:NASICON;hot pressing;interfacial resistance;Li-ion conductivity;all-solid-state batteries