Freestanding Hierarchically Sandwich-Like TiS ₂-TiO ₂/MXene Film as Bi-Functional Interlayer for Stable Li-S Batteries

Abstract

Lithium-sulfur battery (LSB) is considered a kind of potential energy storage systems on account of its high theoretical capacity (1675 mAh·g^-1) and energy density (2500 Wh·Kg^-1). However, poor ionic/electronic conductivity and annoying shuttle effects still need to be resolved. Here a highly flexible and highly conductive MXene (Ti₃C₂T_x) interlayer with a sandwich structure is reported, the surface of which is a TiS₂/TiO₂ heterostructure formed by vulcanized. In this framework, the role of TiO₂ nanoparticles is adsorbent to combine the lithium polysulfides (LiPSs), and the TiS₂ nanoparticles function as catalysts to further facilitate the conversion of long-chain LiPSs to short-chain Li₂S₂/Li₂S under the high conductivity of Ti₃C₂T_x. Furthermore, the interlayer can protect the Lithium metal anode by preventing polysulfide from depositing on the anode surface. Accordingly, the TOS/MX/TOS interlayer exhibits excellent performance with stable long-term cycling (≈76.1% capacity retention with a decay rate of 0.048% per cycle after 500 cycles at 1C). This sandwiched interlayer with high discharge capacity and steady cycling performances is conducive to the practical application of lithium-sulfur batteries.

Keywords: free-standing, MXene, lithium-sulfur battery, sandwich-like