Fe3C@NCNT as a promoter for the sulfur cathode toward high-performance lithium-sulfur batteries

Abstract

Rechargeable Lithium-Sulfur batteries (LSBs) are widely investigated as one of the most promising electrochemical energy storage devices due to their high energy density, low cost and environmental benignancy. However, poor conductivity, insufficient adsorption strength and sluggish multi-electron redox reactions restrict LSBs performance. Thus rational design of one–dimensional materials with good conductivity for sulfur, strong adsorption and catalytic abilities to lithium polysulfides (LiPSs), is necessary for improving the electrochemical behavior of lithium-sulfur batteries. Herein, we report Fe3C nanorods encapsulated in nitrogen-doped carbon nanotube (Fe3C@NCNT) as a promoter for sulfur cathode, in which CNT acting as a conductive network promotes ionic and electronic transfer, while “lithiophilic” heteroatom N immobilizes LiPSs through strong chemical bonding (Li–N bonds), and Fe3C accelerates the adsorption and conversion of LiPSs derived from its catalytic Fe3C site. Therefore, the Fe3C@NCNT as a promoter prolong the life of LSBs with the help of the synergistic effect of polarized N heteroatoms and catalytic effect of Fe3C. As a result, the composite cathode material delivers an outstanding initial capacity of 950 mAh g−1 at 0.5 C, and a capacity of 870 mAh g−1 after 100 cycles. This work proposes a feasible strategy to immobilize LiPSs and accelerate the conversion of LiPSs in high-performance lithium-sulfur batteries.