Green synthesis of S-doped carbon nanotubes via gaseous post-treatment and their application as conductive additive in Li ion batteries

Abstract

Sulfur-doped carbon nanotubes (SCNTs) exhibit better conductivity and hydrophilicity, as compared to the undoped carbon nanotubes (CNTs). Low cost mass production of SCNTs is highly desirable for their real application at an industrial scale. Here, scalable green syntheses of SCNTs and S, N dual doped CNTs (SNCNTs) are demonstrated based on the gaseous S doping using SO2 as dopant. The process not only significantly promotes the hydrophilicity and conductivity of CNTs due to the incorporation of S atoms in carbon framework, but also purifies the final product due to burning off the carbon coatings of metal particles. SO2 is generated by CaSO3 pyrolysis and absorbed by CaO, thus realize the recycling of S species. The LiFePO4 cathodes using the as-prepared SCNTs and SNCNTs as conductive additive exhibit enhanced capacity and rate performance than the electrodes prepared with the pristine CNTs, not matter using N-methyl pyrrolidone or water as solvent.