Sb-doped Li10GeP2S12-type electrolyte Li10SnP2-xSbxS12 with enhanced ionic conductivity and lower lithium-ion migration barrier

Abstract

Li10SnP2S12 (LSPS) has been regarded as a promising solid electrolyte because of its higher ionic conductivity and lower cost. In this work, P sites of LSPS are partially substituted with Sb by the solid-phase sintering method. A series of Li10SnP2-xSbxS12 (0 ≤ x ≤ 0.4) solid electrolytes are prepared. Among them, the ionic conductivity of the Li10SnP1.8Sb0.2S12 solid electrolyte reaches 2.43 mS cm−1. Through X-ray diffraction and refinement analysis, it is found that Sb successfully substituted part of P and increased the lattice constant. Through temperature-dependent alternating current impedance experiments and density functional theory calculations, it is found that the main reasons for the increase in ionic conductivity are the reduction of activation energy and the energy barrier of the Li+ migration path around Sb. The improved air stability of the electrolyte after Sb doping conforms to the Hard-Soft-Acid-Base theory. Furthermore, the assembled all-solid-state battery with Li10SnP1.8Sb0.2S12 exhibits a high specific capacity and good cycling stability than LSPS.