Molybdenum carbide nanoparticles encapsulated in N-doped carbon nanotubes as a sulfur host for advanced Li-S battery

Abstract

The poor electrical conductivity of sulfur, large volume expansion, shuttle effect, and sluggish redox reactions in Li–S battery limit their practical application. Mo2C nanoparticles encapsulated in N-doped carbon nanotubes (Mo2C/NC NTs) were synthesized using MoO3 nanorods as templates through a polypyrrole coating, heating, ammonia washing, and high-temperature carbonization. The Mo2C/NC NTs had a hollow structure with high specific surface area that can alleviate the volume expansion of cathode and the shuttle effect of polysulfides. The encapsulated Mo2C nanoparticles could anchor the lithium polysulfides and increase electrochemical reaction kinetics. Mo2C/NC NTs combined with sulfur (Mo2C/S/NC NTs) exhibited 400.2 mAh g−1 over 500 cycles at 1.0 A g−1 with a capacity decay rate of 0.068% per cycle. Density-functional theory calculations and X-ray photoelectron spectroscopy confirmed that Mo2C/NC NTs could anchor polysulfides and alleviate the shuttle effect by chemical interactions. This study supplies a novel route to prepare nanoparticle-encapsulated in N-doped carbon nanotubes for advanced Li-S battery.