Preparation and electrochemical performance of imidazole-based poly(ionic liquid)-derived solid electrolytes for stable lithium metal batteries

Polyionic liquid (PIL) -based solid electrolytes have great potential in solid-state lithium metal batteries due to their safety and film-forming property. To break the “trade-off” effect among ionic conductivity, lithium-ion transference number, and mechanical strength in a single system, a modification strategy that combines molecular structure design with in-situ cross-linking strategy was proposed. Specifically, we synthesized imidazole-based ionic liquid monomers (DMImTFSI) with acetal moieties on the side chain and introduced triacrylate of ethoxylated trimethylolpropane (ETPTA) as a crosslinker for in-situ polymerization to prepare the solid-state electrolyte (DE-SPE). The acetal groups in DMImTFSI promote the dissociation of lithium salts, while the cross-linked network constructed by ETPTA enhances mechanical strength. Meanwhile, the synergistic coordination of C=O and ether oxygen groups within ETPTA increases the lithium-ion transference number (0.56) and reduces the activation energy (E a = 0.38 eV). The assembled Li|DE-SPE|Li battery maintains a stable overpotential of 120 mV after 2000 h under 0.1 mA cm −2 . This study not only clarifies the electrochemical enhancement mechanism of DE-SPE but also provides new design ideas for the development of intrinsic-safety and high-performance solid polymer electrolytes.