Mechanically reinforced solid-state polymer electrolyte using illite filler for flexible all-solid-state Li-metal batteries

Solid-state electrolytes have attracted significant attention due to their high safety, mechanical stability, and compatibility with lithium metal anodes, making them a critical component in the development of next-generation all-solid-state batteries. Polymer-based solid electrolytes (PSEs) offer advantages such as flexibility, processability, and good interfacial contact with electrodes but suffer from low structural stability. In this study, PSEs were fabricated by photopolymerization from ethoxylated trimethylolpropane triacrylate and expanded illite (EI) functional filler. The PSEs synthesized with 4 wt% EI show a favorable ionic conductivity of 2.31 × 10⁻⁴ S cm⁻¹ at 25 °C and an all-solid-state Li/NCM622 coin cell using the PSE as the electrolyte delivered a discharge capacity of 129.5 mAh g⁻¹ at 0.1C with 98 % Coulombic efficiency. In addition, the EI-containing PSE exhibited improved mechanical strength, enabling the fabrication of a flexible all-solid-state Li-metal battery pouch cell. This study offers valuable insight into the design of PSEs using clay-based fillers.