A robust sulfur host with dual lithium polysulfide immobilization mechanism for long cycle life and high capacity Li-S batteries

Beyond the physical lithium polysulfide (Li₂S_x) entrapment of various 3D porous sulfur hosts, the importance of chemical interactions between sulfur host and Li₂S_x on performance of Li-S batteries has recently been highlighted. However, most of these studies focus mainly on one type of chemical interaction and effective suppression of Li₂S_x migration is still lacking. Here, we report a uniquely designed sulfur host that can immobilize Li₂S_x through a dual chemisorption mechanism. The new sulfur host is consisted of an MXene matrix and polydopamine (PDA) overcoat, where Mxene forms a strong Ti–S bonding by the Lewis acid-base mechanism while PDA withholds Li₂S_x through the polar-polar interaction. Benefited from the double chemisorption, the new cathode with a high sulfur loading of 5 mg cm⁻² has been demonstrated with an initial capacity of 1001 mA h g⁻¹ at a capacity retention of 65% over 1000 cycles at 0.2 C. Overall, this study not only presents a unique chemical mechanism to entrap Li₂S_x, but also provides a new way to rationally design a practical sulfur cathode for high-performance Li-S batteries.