The Enhanced Performance of Polyethylene Composite Separators by the Modification of Lithium Salt@SiO2 Nanoparticles

Abstract Improving the dimensional thermal stability and electrochemical performance of polyethylene (PE) membrane is critical to enhance the safety performance of lithium‐ion battery. In this paper, PE membranes are modified by lithium bis(trifuoromethanesulfonyl)imide (LiTFSI) solution and then coated with nano‐SiO 2 /polyvinyl alcohol solution to obtain composite membranes (PE@L n SiO 2 , where n represents the concentration of LiTFSI solution). The obtained PE@L4SiO 2 (LiTFSI solution concentration is 4%) composite membrane possesses a thermal shrinkage rate of only 17% at 150 °C, which is far superior to that of the PE separator. The ionic conductivity of the composite membrane is 16.9 × 10 −4 S cm −1 at room temperature (RT), and the battery impedance decreases to 154 Ω, which is remarkably better than that of the PE membrane (188 Ω). The battery delivers a reversible discharge capacity of 164 mAh g −1 at 0.2 C under RT after 250 cycles, and the coulomb efficiency remains above 99%. The battery also has a high discharge capacity of 132 mAh g −1 at 2 C, which indicates that it has excellent rate performance. Therefore, this research successfully explores a simple method to effectively improve the dimensional thermal stability of PE separator, as well as the electrochemical and safety performance of lithium battery.