Ketjen Black–titanium dioxide coated glass fiber separator for high performance Li/S cells using bare sulfur cathode

Sulfur is considered as one of the promising cathode candidates for the next generation secondary batteries due to its high theoretical capacity. Several issues, such as the insulation of sulfur and the shuttle effect caused by highly soluble polysulfides, are alleviated by encapsulating sulfur into a conductive framework. However, those methods inevitably sacrifice both the gravimetrically and volumetrically energy density of the fabricated cells. In this context, the issues mentioned above are ameliorated via a commercial Glass Fiber membrane coated with Ketjen Black (KB, commercial EC 600 JD) and titanium dioxide (TiO ₂ ) as the separator. Bare sublimed sulfur is employed as the cathode. When being cycled at 0.2 C, the Li/S cell, using the membrane coating 20 wt% TiO ₂ and 50 wt% KB as separator, presents 1196 and 729 mAh g ⁻¹ in the 1st and 200th cycle, respectively. Even being cycled at 2 C, the cell still shows 531 mAh g ⁻¹ reversible capacity after 100 cycles. Such good performance could be attributed to: (1) the highly conductive KB within the coated layer offers additional electron pathways covering the top surface of the bare sulfur cathode and (2) the coated layer can form chemical binding with lithium polysulfides via TiO ₂ and physically adsorb the lithium polysulfides through KB, both alleviating the shuttle effect.