Fluorine-Doped Electrolyte and Artificial SEI for Enhanced Interfacial Stability in All-Solid-State Lithium Metal Batteries

The poor lithium metal/solid electrolyte (SE) interface compatibility presents a considerable obstacle in the progression of all-solid-state lithium metal batteries (ASSLMBs). Constructing a robust solid electrolyte interphase (SEI) offers a favorable approach to alleviating these difficulties. Herein, we propose a dual strategy involving fluorine-doped electrolyte and artificial SEI to improve the lithium metal/Li5.5PS4.5Cl1.5 (LPSC) interface stability. X-ray photoelectron spectroscopy (XPS) results unveil the formation of a LiF-rich interphase at the SE/Li metal interface, facilitated by the reaction of Li metal with an F-doped electrolyte and fluoroethylene carbonate (FEC) treatment on the Li metal surface (FEC@Li). The F-doped electrolyte Li5.5PS4.5Cl1.45F0.05 (LPSCF-0.05) maintains a high ionic conductivity of 6.37 mS cm(-1) at room temperature. Consequently, the critical current density (CCD) of the Li metal symmetric cell reaches 3.52 mA cm(-2). Full cells assembled with NCM622, LPSCF-0.05, and FEC@Li exhibit superior cycling and rate performances along with excellent low-temperature performance. The battery delivers a high initial discharge capacity of 172.6 mAh g(-1) at 0.2C under room temperature, cycling steadily for over 100 cycles. Under a high C-rate of 2C and a low temperature of -20 degrees C, the batteries display high capacities of 117.7 and 139.0 mAh g(-1), respectively. This study offers an effective way of constructing high-performance ASSLMBs.