Immobilization and Kinetic Acceleration of Lithium Polysulfides by Iodine-Doped MXene Nanosheets in Lithium–Sulfur Batteries

Abstract

Inhibiting the shuttle effect and accelerating the reaction kinetics of soluble lithium polysulfides (LiPS) are crucial for constructing high-performance lithium–sulfur (Li–S) batteries. Herein, a novel iodine-doped MXene (I-MXene)-modified separator is proposed to optimize the electrochemical performance of Li–S batteries. The I-MXene composite exhibits a uniform two-dimensional layer structure and high electronic conductivity, which are beneficial for building high conductivity and a thin/uniform coating layer. Additionally, the I-MXene can effectively immobilize LiPS through Ti–S bonds and accelerate the reaction kinetics of LiPS conversion. When combined with the KB/S cathode, the cell using the I-MXene-modified separator displays a high initial discharge capacity of 1308 and 761 mAh g–1 after 100 cycles at 0.2 C, as well as high C-rate capability (655 mAh g–1/2 C). With a sulfur area loading above 5 mg cm–2, the cell matching the I-MXene/PP separator still delivers an attractive reversible capacity of 578 mAh g–1 after 200 cycles at 0.2 C. The novel catalytic two-dimensional materials and separator modification method proposed here are expected to facilitate the practical application of Li–S batteries.