Hybrid separator containing reactive, nanostructured alumina promoting in-situ gel electrolyte formation for lithium-ion batteries with good cycling stability and enhanced safety

The thermal instability of conventional polyolefin separators and the high flammability of organic electrolytes are the primary safety-related concerns of high-energy-density lithium-ion batteries. To address these issues, reactive Al2O3 nanostructured materials are coated onto a polyethylene (PE) separator to promote the formation of gel electrolyte and enhance the thermal stability of the separator. The Al2O3 nanostructured materials are surface-treated by 3-methacryloxypropyl trimethoxysilane to induce radical polymerization with tetra(ethylene glycol) diacrylate (TEGDA) in liquid electrolyte. The three-dimensional network formed by cross-linking reactive alumina nanostructured materials and TEGDA reduces the electrolyte leakage from the cell and enhances the interfacial adhesion between separator and electrodes. Thermal shrinkage of the reactive alumina-coated separator is also significantly reduced at 140 °C, providing enhanced thermal stability. In addition to improved thermal safety, lithium-ion cells employing a reactive alumina-coated PE separator exhibit stable cycling at both ambient and high temperatures. •Reactive alumina-coated separator is prepared to promote gel electrolyte formation.•Thermal stability of alumina-coated separator is significantly enhanced at 140 oC.•The cell with reactive separator exhibits good cycling stability and enhanced safety.•The reactive Al2O3 coated-separator is promising for enhancing the battery safety.