AlF3 coating as sulfur immobilizers in cathode material for high performance lithium-sulfur batteries

Abstract

Although the rechargeable lithium-sulfur battery is an advanced energy storage system, their practical implementation has been impeded by many issues, in particular the ‘shuttle effect’ causing rapid capacity fade and low coulombic efficiency. Herein, the AlF3 coating, prepared via a facile solution-based method, is used as sulfur immobilizers in cathodes for Li–S batteries for the first time. The physical confinement, chemical anchoring and catalysis conversion for polysulfide are achieved simultaneously through the existence of the AlF3 coating, which is confirmed by experimental results. Meanwhile, the CNTs improved the electrical conductivity of composite materials significantly, and a suitable three-dimensional conductive framework was formed to accommodate sulfur. Due to these merits, the as-designed composite materials of carbon nanotubes-sulfur coating by aluminum fluoride (CNTs-S@AlF3) cathode exhibited excellent electrochemical properties and stable capacity retention. The initial discharge capacity reaches 1144.1 mAh g−1 and after 250 cycles is 783 mAh g−1 at 1 C, which is much higher than the composite materials of without AlF3 coating. Moreover, the CNTs-S@AlF3 cathode presents excellent long-term capacity stability with a capacity decay of 0.062% per cycle during 1000 cycles at 0.5 C, offering a potentiality for use in high energy Li–S batteries.