Thin-film type in situ polymerized composite solid electrolyte for solid-state lithium metal batteries

Solid-state batteries (SSBs) using composite solid electrolytes (CSE) have attracted attention as next-generation battery materials with high stability and energy density. In this study, we manufactured CSE using a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) polymer host and ceramic inorganic filler. Next, a 23.3 mu m electrolyte was prepared via in situ polymerization using a poly(ethylene glycol) methyl ether acrylate (PEGMEA)-based liquid precursor. The introduction of ceramic fillers and in situ polymerization can improve the mechanical strength and ionic conductivity of the electrolyte and enable a high lithium transference number owing to the anion immobilization effect. LiFePO4/Li cells using the manufactured electrolyte exhibited a high capacity maintenance rate of 93.2% over 150 cycles. In addition, a pouch cell based on the prepared electrolyte exhibited excellent stability and flexibility.