Design of a 3D CNT/Ti₃C₂T_x aerogel-modified separator for Li–S batteries to eliminate both the shuttle effect and slow redox kinetics of polysulfides

Lithium–sulfur (Li–S) batteries suffer from fast capacity fade and an inferior rate performance due to the shuttling of polysulfides (LiPSs) and slow redox kinetics. To solve these issues, a three-dimensional (3D) CNT/Ti₃C₂T_x aerogel was prepared, with Ti₃C₂T_x as the active matrix and CNTs as the conductive pillars, and used as a LiPS immobilizer and promoter to modify a commercial Li–S battery separator. The unique design of highly porous 3D aerogel results in the exposure of more Ti₃C₂T_x active sites by preventing the restacking of their sheets, which not only provides abundant charge transport paths, but also strengthens the adsorption and catalytic conversion of LiPSs. The incorporation of CNTs forms a highly conductive network to connect the adjacent Ti₃C₂T_x sheets, thereby improving the conductivity and robustness of the 3D aerogel. As a result, a Li–S cell using the CNT/ Ti₃C₂T_x aerogel-modified separator has a high rate capacity of 1 043.2 mAh g⁻¹ up to 2 C and an excellent cycling life of over 800 cycles at 0.5 C with a low capacity decay rate of 0.07% per cycle.