Multiple roles of titanium carbide in performance boosting: Mediator, anchor and electrocatalyst for polysulfides redox regulation

Abstract

The lithium-sulfur batteries (LSBs) have attracted more and more attention in recent years owing to its high theoretical energy density, abundant sulfur source and relatively low cost. However, the serious polysulfides shuttle and sluggish sulfur redox kinetics hinder the development and commercial application of high-performance lithium-sulfur batteries. In this paper, the titanium carbide (TiC)-decorated carbon matrix is considered as the mediator, anchor and electrocatalyst for polysulfides redox reaction. It has been proved that the conductive and polar titanium carbide can not only chemisorbs lithium polysulfides via titanium-sulfur (Ti-S) coordination, but also optimize the lithium sulfide (Li2S) nucleation/precipitation mechanism for better redox reaction. Especially, the graphene oxide and carbon nanotube matrix (GO-CNT) in this case can act as both host for Li2S loading and TiC precipitation. Accordingly, the as-fabricated lithium sulfide-graphene oxide–carbon nanotube-titanium carbide (LS-GO-CNT-TiC) cathode delivers the high initial discharge capacity of 956 mAh g−1 at 0.1C and good rate capability of 508 mAh g−1 at 2C. These results consequently manifest that the conductive and polar matrix of LS-GO-CNT-TiC can perform as a promising cathode of the high performance LSBs.