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 (Li₂S_n, 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.