One-step synthesis of Bi2Se3@CoSe carbon nanotubes composite as efficient sulfur host for accelerating catalytic conversion of polysulfides

Abstract

The controversial lithium-sulfur (Li-S) batteries still have too many challenges to be commercially developed. The electrical conductivity of elemental sulfur is poor. Moreover, the shuttle effect caused by soluble polysulfides can reduce sulfur utilization and produce lithium dendrites at the anode. To address the above disadvantages, Bi2Se3@CoSe composite is in-situ synthesized on carbon nanotubes through one-step hydrothermal method and applied to the cathodes. The strong metallicity of Bi2Se3@CoSe composite improves the electrical conductivity. In comparison with pure metal selenides, the attached CoSe particles on lamellar Bi2Se3 surface increase the adsorption sites of lithium polysulfides to effectively alleviate the shuttle effect. Combined with these advantages, S/Bi2Se3@CoSe/CNTs cathode exhibits a long cycling stability. Over 700 cycles, the cathode shows a capacity decay rate of 0.049 % per cycle at 0.5 C. In addition, the cathode shows high initial capacity (840.4 mA h g−1) with sulfur content of 2.31 mg cm−2 at 0.1 C. This study demonstrates the efficacy of Bi2Se3@CoSe composite in improving the conductivity of the sulfur cathodes and polysulfides chemisorption.