Li1.75Zr0.75Sb0.25Cl4.75O0.625 Oxyhalide Solid Electrolyte: Enhancing Performance by Regulating Phase Transition

Abstract

New types of halides have garnered significant attention from researchers in the development of high-performance all-solid-state lithium-ion batteries due to their exceptional high-potential stability, high ionic conductivity, and favorable mechanical properties. Here, a mechanochemical ball milling method is employed to synthesize the Li_2–2xZr_1–2xSb_2xCl_6–10xO_5x material by incorporating an appropriate amount of Sb–O into Li₂ZrCl₆. Experimental results and Rietveld refinement confirm the successful synthesis of a zirconium-based chloride-oxide solid electrolyte material (Li_1.75Zr_0.75Sb_0.25Cl_4.75O_0.625). Due to the incorporation of Sb⁵⁺, which has a smaller ionic radius but a higher valence state, the volume of the condensed crystal lattice decreased, while the number of lithium vacancies increased. The incorporation of O^2– induced a phase transition in the crystal structure, leading to the redistribution of lithium ions. The combined effects of these factors enhanced the ionic conductivity. The lithium-ion conductivity of the electrolyte at 25 °C is 4.2 × 10^–4 S cm^–1, and it possesses a wide electrochemical stability window (1.22–4.62 V vs Li⁺/Li). Simultaneously, Sb–O dual doping enhances the electrochemical reduction stability of Li₂ZrCl₆. The all-solid-state battery utilizing Li_1.75Zr_0.75Sb_0.25Cl_4.75O_0.625 as the electrolyte and sc-NCM811 as the cathode demonstrates excellent cycling performance and a high capacity retention rate. These investigations offer a promising strategy for the rational design of zirconium-based halide solid-state electrolytes, which are essential for the development of high-performance all-solid-state batteries.