Fluoroethylene carbonate-Li-ion enabling composite solid-state electrolyte and lithium metal interface self-healing for dendrite-free lithium deposition

Solid-state Li-metal batteries have attracted much attention owing to the high energy density and safety afforded by Li-metal anode and solid-state electrolytes. However, Li-dendrite penetration and unstable interface between solid-state electrolyte and Li-metal incumber their application. Herein, fluoroethylene carbonate (FEC) added Li0.35La0.55TiO3-Poly (ethylene oxide) (LLTO-(PEO-FEC)) composite solid-state electrolytes (CSSEs) are fabricated to address the bottlenecks. The CSSE possesses high Li+ conductivity of 1.13 × 10−4 S·cm−1 vs low electronic conductivity of 1.68 × 10−9 S·cm−1 at 25 °C, presents a wide electrochemical window of 5.2 V (vs. Li+/Li), and shows much more stable lithium deposition at current density of 0.2 mA·cm−2 for 800 h. FEC is driven by Li+ to the damaged interface to form new LiF-rich interface layer, which enables the self-healing of Li-metal and CSSE interface and enhances the electrochemical stability of CSSEs against Li-metal. Li| (LLTO-(PEO-FEC)) |LiFePO4 cell presents discharge capability of about 115 mAh·g−1 after 100 cycles at 50 °C. This work reveals the mechanism of dendrite-free Li deposition via interface self-healing process under the effect of FEC–Li+ coordination and provides a promising way to prepare the high performances composite solid-state electrolytes and to fabricate the dendrite-free all-solid-state lithium battery.