Enhancing the performance of separator for Li-S battery via initiated chemical vapor deposition(iCVD) process

Abstract

Lithium-sulfur (Li-S) battery can utilize abundant sulfur which is produced as 70 million tons every year during oil refining process, it has affordable price and eco-friendly characteristic. Li-S battery also has high theoretical capacity density(1167mAh/g) and energy density (2600Wh $kg^{-1}$), it has been considered as next-generation battery. In despite of these advantages, Li-S battery has very poor stability due to several problems, ‘shuttle effect’ which is that soluble lithium polysulfide (LiPS) from sulfur cathode decrease Coulombic efficiency (CE) have remained the important problem to solve. In this paper, we succeeded to modify separator to suppress that soluble LiPS moves to anode via initiated chemical vapor deposition(iCVD) process. We used poly vinyl imidazole(pVIDZ) for modifying separator, we minimized loss of energy density because ultra-thin and 0.055mg$cm^{-2}$ pVIDZ was coated on polypropylene separator(pVIDZ@PP) by one-step via iCVD process. When pVIDZ@PP was used for Li-S battery separator, it showed an outstanding performance of a high capacity of 906 mA h $g^{−1}$ and it maintained specific capacity of 506 mA h $g^{−1}$ after 900 cycles. This result offers new method to modify separator by one step with minimizing loss of energy density.