Molecular-Level designed gel polymer electrolyte with ultrahigh lithium transference number for high-performance lithium metal batteries

The heterogeneous migration of dual ions within the gel polymer electrolytes (GPEs)-based lithium metal batteries leads to significant concentration polarization and compromises interfacial stability during cycling. Therefore, an in-situ GPE (BAEDA-PETEA-LE-PAN) is fabricated in polyacrylonitrile (PAN) porous membrane, with the benzene ring-containing bisphenol A ethoxylate diacrylate (BAEDA) oligomer and the pentaerythritol tetraacrylate (PETEA) monomer serving as the polymer backbone. BAEDA engages in multi-site adsorption interaction with the lithium salt anion, while simultaneously exhibiting mild coordination interaction with Li+. This intermolecular interaction restricts the migration of the anion and increases the ionic transfer number of BAEDA-PETEA-LE-PAN (tLi+ = 0.93). As expected, the Li|BAEDA-PETEA-LE-PAN|Li battery demonstrates exceptional cycling performance with an extended lifespan of approximately 1400 h while maintaining a negligible overpotential of only 8 mV at a current density of 0.05 mA cm- 2. Also, NCM811|BAEDA-PETEA-LE-PAN|Li battery exhibits stable operation for 200 cycles at a rate of 3C with a capacity retention of 83 %. This study presents a novel design philosophy for the development of in-situ formation GPEs in high-energy-density lithium metal batteries.