TiO2/Porous Carbon Composite-Decorated Separators for Lithium/Sulfur Battery

The practical application of lithium/sulfur (Li/S) batteries is hindered by the migration of soluble polysulfides (Li2Sn, 4 ≤ n ≤ 8) from cathode to anode, leading to poor electrochemical stability of the cell. To address this issue, in the present study, a TiO2/porous carbon (TiO2/PC) composite-coated Celgard 2400 separator was successfully fabricated and used as a polysulfide barrier for the Li/S battery. In TiO2/PC, the highly conductive PC with three-dimensional ordered porous structure physically constrains polysulfides and at the same time serves as an additional upper current collector. On the other hand, the TiO2 on the surface of PC chemically adsorbed polysulfides during the charge/discharge process. Due to the physical and chemical adsorption properties of TiO2/PC composite coating layer, an initial discharge capacity of 926 mAh g−1 at 0.1 C and a low fading rate (75% retention after 150 cycles) were achieved. Moreover, in the rate capability test, the discharge capacity for the TiO2/PC-modified Li/S battery was recovered to 728 mAh g−1 at 0.1 C after high-rate cycling and remained ~ 88% of the initial reversible capacity.