Safety and performance enhanced boehmite-coupled polyethylene nanocomposite separator for lithium-ion batteries by synergetic effects of silane treatment and electron irradiation

Separators are among the key components affecting both the safety and performance of batteries. Herein, boehmite-coupled high-density polyethylene (HDPE) nanocomposite separators with enhanced safety and per-formance are prepared via silane treatments and electron irradiation. The silane treatment of boehmite nano-particles (BNPs) leads to the homogeneous dispersion of the BNPs in HDPE owing to the spacer alkyl groups in silane. Electron irradiation induces chemical coupling between the silane-treated BNPs and HDPE, as well as the crosslinking of HDPE. Electron irradiation also oxidizes HDPE, improving the electrolyte affinity of the sepa-rators. Consequently, the safety and performance of the separators are significantly improved, and the degree of improvement depends on the type of silane. A nanocomposite separator comprising octadecyl-functionalized BNPs exhibits superior dimensional stability (puncture strength of 0.74 N mu m-1 and thermal shrinkage of 3.2% at 140 degrees C for 30 min). In addition, a nanocomposite separator comprising aminopropyl-functionalized BNPs demonstrates excellent ionic conductivity (1.61 mS cm-1). A lithium-ion cell assembled with the nanocomposite separator has an exceptional rate capability (discharge capacity at 20 C maintains 72.9% of the capacity at 0.5 C) and cyclic stability (discharge capacity retention of 96.2% with a Coulombic efficiency of 99.5% after 100 charge/discharge cycles at 0.5 C).