Electrochemical catalytic interface toward high-energy density lithium-sulfur batteries

Abstract

Lithium-sulfur (Li-S) batteries with lithium sulfide (Li2S) cathodes are promising candidates for next-generation batteries owing to their high energy density and compatibility with lithium-free anode materials. However, Li2S cathodes face challenges arising from high activation energy barriers and the shuttle effect of polysulfide intermediates. Herein, we present an innovative strategy to maximize the energy density and cycle life of Li-S batteries by integrating a pelletized Li2S/graphene-carbon nanotubes (Li2S/Gr-CNTs) composite cathode with a Ti3C2Tx MXene /CNTs composite interlayer (Int. M). Through high-pressure pelletization, the Gr-CNTs physically entrap Li2S particles, confining them within a robust structural framework while preserving excellent electrically conductive pathways. Int. M placed on the surface of the Li2S/Gr-CNTs composite cathode functions as a catalytic interface with strong affinity for polysulfide intermediates and mixed ionic/electronic conducting properties, thereby promoting electrochemical conversion reactions. The integration of Li2S/Gr-CNTs (with 90 wt% Li2S content) with Int. M maintains the ultra-thin electrode thickness of 109 μm and achieves an areal capacity of 8 mAh cm−2 at 0.1 C, resulting in a high volumetric capacity of 734 mAh cm−3. The Li-S full batteries coupling with a graphite anode demonstrate unprecedented capacity retention of ∼80% after 1000 cycles at 0.5 C.