Layer-Structured Composite Solid-State Electrolyte with a Li_1.3Al_0.3Ti_1.7(PO₄)_{3-Coated Separator for High-Voltage Lithium Metal Batteries by In Situ Polymerization}

Thepoor interfacial contact between solid-state electrolytes (SSEs)and electrodes, which hinders the applications of solid-state batteries(SSBs), could be improved by in situ polymerization. However, thelimited electrochemical window and insufficient mechanical strengthof in situ-polymerized electrolytes make them unable to match high-voltagecathodes and inhibit lithium dendrites. Here, a layered organic-inorganiccomposite solid-state electrolyte structure is designed by introducinga Li1.3Al0.3Ti1.7(PO4)(3) (LATP)-coated polyethylene separator and fluoroethylene carbonate(FEC) into in situ-polymerized 1,3-dioxolane (DOL). The high-voltagestable fluoride-rich cathode-electrolyte interface formed insitu by FEC widens the electrochemical window of the composite solid-stateelectrolyte. In addition, the LATP coating layer inhibits the growthof lithium dendrites and increases the Li-ion conductivity by reactingwith FEC to generate FEC derivatives. The Li/LiCoO2 batteryexhibits good cycling and rate performance with a cutoff voltage of4.3 V at room temperature. It provides a simple and practical solutionto improve the performance of high-voltage lithium metal batteriesbased on in situ polymerization.