A multi-layered Ti3C2/Li2S composite as cathode material for advanced lithium-sulfur batteries

Abstract

Abstract Lithium-sulfur (Li-S) batteries with lithium sulfide (Li2S) as cathode have attracted great attention recently, because of high specific capacity (1166 mA h g−1) of Li2S and potential safety of using Li metal-free anode. Li2S cathode has lower volume expansion and higher thermal stability than the traditional sulfur cathode. However, the problems of “shuttle effect” and poor electrical conductivity of the cathode material still need to be overcome. In this work, multi-layered Ti3C2/Li2S (ML-Ti3C2/Li2S) composite has been prepared and applied as a cathode in advanced Li-S batteries. The unique multi-layer sheet structure of Ti3C2 provides space for the storage of Li2S, and its good conductivity greatly enhances the usage ratio of Li2S and improves the conductivity of the whole Li2S cathode. Compared with commonly used graphene, ML-Ti3C2 can trap polysulfides effectively by chemical adsorption and also activate the reaction of Li2S to polysulfides by forming Ti-S bond. As a result, during the cycling of the batteries with ML-Ti3C2/Li2S cathodes, the activation voltage barrier of the first cycle has decreased to 2.8 V, and the “shuttle effect” has been suppressed effectively. The cycling and rate performances of the ML-Ti3C2/Li2S cathodes have been significantly improved compared to that of graphene/Li2S cathodes. They maintain a capacity of 450 mA h g−1 at 0.2 C after 100 cycles, and deliver attractive rate performances of 750, 630, 540, 470 and 360 mA h g−1 at 0.1 C, 0.2 C, 0.5 C, 1 C, and 2 C, respectively.