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

Abstract

Beyond the physical lithium polysulfide (Li2Sx) entrapment of various 3D porous sulfur hosts, the importance of chemical interactions between sulfur host and Li2Sx 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 Li2Sx migration is still lacking. Here, we report a uniquely designed sulfur host that can immobilize Li2Sx 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 Li2Sx 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 Li2Sx, but also provides a new way to rationally design a practical sulfur cathode for high-performance Li-S batteries.