SiO2 doped halogen-rich argyrodites for high-performance all-solid-state lithium–sulfur batteries

Abstract

The argyrodite-type sulfide electrolytes (Li₆PS₅X, X = Cl, Br, I) have demonstrated numerous benefits for high-performance and secure all-solid-state lithium‑sulfur batteries (ASSLSBs). These advantages include their rapid lithium (Li) ion conduction and exceptional compatibility with the anode. Nevertheless, despite these benefits, the key obstacles for their implementation are the need for higher room-temperature ionic conductivity, improved air/moisture compatibility, and enhanced electrochemical stability. In this study, we propose a halogen-rich argyrodite (Li_5.3PS_4.3Cl_1.7-xBr_x) to obtain ultrafast ionic conductivity at ambient temperature. To enhance the ionic transport channel, the anion disorder on the site is optimized and the Li vacancies in the structure are increased by substituting anions with halogens (Cl/Br). The Li_5.3PS_4.3Cl_0.85Br_0.85 is synthesized effectively by a high-energy ball milling process, resulting in a remarkable ionic conductivity of 9.07 mS⋅cm⁻¹ at room temperature. In addition, a SiO₂ dopant is utilized to strengthen the lattice structure of the solid-state electrolyte (Li_5.3+ySi_yP_1-yS_4.3-2yO_2yCl_0.85Br_0.85) in order to improve its resistance to air/moisture and enhance its electrochemical stability within specific voltage ranges. The Li_5.4Si_0.1P_0.9S_4.1O_0.2Cl_0.85Br_0.85 with optimized composition demonstrates an ionic conductivity of 8.2 mS⋅cm⁻¹ at room temperature and exceptional stability in air. The ASSLSBs containing Li_5.4Si_0.1P_0.9S_4.1O_0.2Cl_0.85Br_0.85 exhibit impressive specific capacities of 1191 mAh⋅g⁻¹ (0.1C after the initial cycle) and 989 mAh⋅g⁻¹ (0.1C after 100 cycles) at room temperature. Additionally, they demonstrate significant cyclability (83.04 % after 100 cycles) and excellent Coulombic efficiency (>99.5 %). This study presents a novel strategy to promote the application of sulfide electrolytes in fabricating ASSLSBs.