Catalytic cobalt phosphide Co2P/carbon nanotube nanocomposite as host material for high performance lithium-sulfur battery cathode

Highlights: • Catalytic Co₂P synthesized by hydrothermal method and grown on carbon nanotube materials with good conductivity at the same time, forming CNT-Co₂P-n composites as host materials for sulfur. • The Co₂P nanoparticles catalyze the conversion of the dissolved polymer lithium sulfide into solid Li₂S₂/Li₂S, which suppresses the shuttle effect and enhances the kinetics of the redox reaction. • Composite cobalt phosphide on carbon nanotubes can not only improve the specific capacity of the material, but also improve the cycle stability of the material. -- Abstract: Lithium-sulfur batteries are one of the most promising cathode materials for next-generation lithium-ion batteries, but there are still having some problems, for example, poor electrical conductivity, slow shuttle effect, and slow electrochemical reaction kinetics. In this paper, carbon nanotubes materials with good conductivity are used as the substrate. Co₂P with catalytic function is grown on the surface of carbon nanotubes by hydrothermal method as the host material of lithium-sulfur batteries. It is characterized by XRD, SEM, TEM, XPS and element mapping. The results showed that Co₂P was successfully synthesized on the surface of carbon nanotubes. The study found that the addition of Co₂P can promote the conversion of Li₂S₆ to Li₂S₄ and Li₂S₄ to Li₂S₂/Li₂S, and inhibit the shuttle-through effect, improve the cycle stability of lithium-sulfur batteries, and the initial capacity reaches 1372 mAh/g at a current density of 0.1 C, the coulomb efficiency is above 96% with cycled 200 times at a current density of 0.2 C.