TiO2 nanotube/RGO modified separator as an effective polysulfide-barrier for high electrochemical performance Li-S batteries

The “shuttle effect” in lithium-sulfur cell causes the terrible cycles stability, that hinders the Li-S batteries served as the next generation high energy density batteries. To address the issue, we investigated that anatase/bate crystal phase titanium dioxide nanotubes (TiO2 NTs) combined with reduced graphene oxide (RGO) to modify the initial polypropylene separator. The TiO2 NTs/RGO film not only localizes the migrating polysulfides by the common effects of chemical binding and physical adsorption but also enhances the lithium-ion migration by reducing the electrochemical resistance. The excellent chemical and physical adsorption ability were proved by the measurement of the X-ray photoelectron spectroscopy and adsorption experiments. The fast lithium-ion migration was analyzed by the diffusion experiment and electrochemical impedance systems. The outstanding initial discharge capacity of 1303.3 mAhg−1 at 0.2 C, which was 78% of the theoretical capacity. Over 100 cycles, the cell with TiO2 NTs/RGO coating separator still retained 620.6 mAhg−1 discharge capacity. The TiO2 NTs/RGO modifying separator exhibits great promise to develop the high energy Li-S batteries.