LAUSR

The coating method of Al2O3 nanoparticles has been widely applied to promote the thermostability and wettability of polyolefin separators. However, the untreated Al2O3/polyethylene (PE) composite separators still need to improve the ionic conductivity (σ) and lithium‐ion transference number (tLi+). Herein, a method is found to obtain amino‐functionalized Al2O3 nanoparticles (N‐Al2O3). As a result, the cell with the N‐Al2O3/PE composite separator has improved σ (0.39 mS cm−1) and tLi+ (0.49). The LiCoO2/Li half‐cell based on N‐Al2O3/PE composite separator exhibits higher discharge capacity (125 mAh g−1) and better cycle performance under the current density of 1 C. Furthermore, the cell containing N‐Al2O3/PE composite separator has a better rate performance and the discharge capacity still maintains 75 mAh g−1 at a high rate of 4 C. This method is effective and simple to modify the PE separator with the amino‐functionalized Al2O3 nanoparticles and enhance the high rate performance of Li‐ion batteries.