Amino‐Functionalized Al2O3 Particles Coating Separator with Excellent Lithium‐Ion Transport Properties for High‐Power Density Lithium‐Ion Batteries

The coating method of Al 2 O 3 nanoparticles has been widely applied to promote the thermostability and wettability of polyolefin separators. However, the untreated Al 2 O 3 /polyethylene (PE) composite separators still need to improve the ionic conductivity ( σ ) and lithium‐ion transference number ( t Li+ ). Herein, a method is found to obtain amino‐functionalized Al 2 O 3 nanoparticles (N‐Al 2 O 3 ). As a result, the cell with the N‐Al 2 O 3 /PE composite separator has improved σ (0.39 mS cm −1 ) and t Li+ (0.49). The LiCoO 2 /Li half‐cell based on N‐Al 2 O 3 /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‐Al 2 O 3 /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 Al 2 O 3 nanoparticles and enhance the high rate performance of Li‐ion batteries.