Yttria-Stabilized Zirconia Nanoparticles─Carbon Nanotube Composite as a Polysulfide-Capturing Lithium–Sulfur Battery Separator

The shuttle phenomenon of polysulfides is a huddle that needs to be overcome to commercialize Li–S batteries. In this study, a composite membrane based on 15 mol % yttria-stabilized zirconia nanoparticles (15YSZ) and carbon nanotubes (CNTs) is coated on a commercial separator (SV718) to fabricate a functional separator that effectively suppresses the shuttle phenomenon while enhancing the performances of Li–S batteries. Compared with the pristine SV718 separator, the functional separator with 15YSZ-CNT composite coating layer significantly enhances the cyclic stability of the Li–S cell by more than 4 times. Furthermore, slight enhancements in specific capacities are observed up to 1C from the Li–S cells incorporating 15YSZ-CNT. The mechanism behind inhibition of the shuttle phenomenon by 15YSZ-CNT is investigated via electrochemical (EIS) and surficial (XPS) characterization, which shows that Frenkel defects, such as oxygen vacancies, in YSZ can effectively capture polysulfides.