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 °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.