Decoration of Silica Nanoparticles on Polypropylene Separator for Lithium–Sulfur Batteries

A SiO 2 nanoparticle decorated polypropylene (PP) separator (PP-SiO 2 ) has been prepared by simply immersing the PP separator in the hydrolysis solution of tetraethyl orthosilicate (TEOS) with the assistance of Tween-80. After decoration, the thermal stability and the electrolyte wettability of the PP-SiO 2 separator are obviously improved. When the PP-SiO 2 separator is used for lithium–sulfur (Li–S) batteries, the cyclic stability and rate capability of the batteries are greatly enhanced. The capacity retention ratio of the Li–S battery configured with the PP-SiO 2 separator is 64% after 200 cycles at 0.2 C, which is much higher than that configured with the PP separator (45%). Moreover, the rate capacity of the Li–S batteries using the PP-SiO 2 separator reaches 956.3, 691.5, 621, and 567.6 mAh g –1 at the current density of 0.2, 0.5, 1, and 2 C, respectively. The reason could be ascribed to that the polar silica coating not only alleviates the shuttle effect but also facilitates Li-ion migration.