2D-2D heterostructure of ionic liquid-exfoliated MoS2/MXene as lithium polysulfide barrier for Li-S batteries

Abstract

Suppressing the dissolution and shuttling of lithium polysulfides (LiPSs) in electrolytes in lithium-sulfur batteries (LSBs) is the focus of researchers. Herein, functional liquid phase exfoliated MoS2 and MXene (IL-MoS2/MX) interlayer is proposed as the separator of LSBs. The unique alternating intercalation structure of the IL-MoS2/MX interlayer provides a channel for ion transport while achieving uniform Li+ deposition on the anode side. Moreover, IL-MoS2 achieves physical and chemical anchoring to LiPSs and lowers the energy barrier for battery reactions. As a result, the separator in the coin cell delivers an initial capacity of 764.4 mAh·g−1 at 1C and high retention of 58.7 % after 700 cycles, with a decay only 0.059 % per cycle. Simultaneously, the excellent stability is also verified under varying current densities. Beyond that, ionic conductivity and lithium-ion migration number are adopted to confirm unique ion transport channels and uniform deposition of lithium. X-ray photoelectron spectroscopy, S8 and Li2S decomposition and nucleation energy barrier analysis are performed to verify the adsorption and catalytic conversion mechanisms. The convenient preparation and excellent performance of IL-MoS2/MX provide a design strategy for functionalized interlayers for LSBs, and the possibility for commercialization.