Fe, Co-bimetallic doped C3N4 with in-situ derived carbon tube as sulfur host for anchoring and catalyzing polysulfides in lithium-sulfur battery

Abstract

Lithium-sulfur battery is regarded as one of the most promising power storage devices on account of the high theoretical specific capacity and high energy density as well as low cost of sulfur. However, during long circulation of lithium-sulfur battery, the inherent polysulfides shuttle effect and the stagnant electrochemical reaction kinetics of lithium polysulfides impede its commercial application. Herein, a bimetallic doping strategy of Fe/Co-C3N4/C is proposed to alleviate shuttle effect and improve electrochemical performance. Owing to high conductivity and large specific surface area as well as abundant active site of Fe/Co-C3N4/C, Fe/Co-C3N4/C/S can boost the adsorption and conversion capability for lithium polysulfides, and thus catalyzing the step-by-step reaction of polysulfides and accelerating the electrode reaction kinetics. It has been found that the lithium-sulfur battery employing Fe/Co-C3N4/C/S as cathode with the sulfur loading of 1.8 mg cm−2 can deliver an initial specific capacity of 949 mAh g−1 at 0.2 C, and maintain a reversible specific capacity of 749 mAh g−1 after 135 cycles with a slow attenuation rate of 0.156% per cycle. Therefore, this bimetallic doping strategy provides a significant exploration for the design of cathode materials of advance high-performance lithium sulfur battery.