Suppressing the Polysulfide Shuttle Effect by Heteroatom-Doping for High-Performance Lithium-Sulfur Batteries

In order to restrict the polysulfide shuttle effect and enhance sulfur utilization of lithium-sulfur batteries (LSBs) especially at low charge/discharge rates, a facile hydrothermal synthesis and subsequent heating melting treatment are used to synthesize the heteroatom-doped carbon nanotubes/sulfur composite cathode. The composition analysis and structure characteristics of samples are examined by X-ray photoelectron spectroscopy, X-ray powder diffraction, and transmission electron microscopy. The electrochemical performances of samples are measured by cyclic voltammetry and charge/discharge experiments. The results show that N, B, S tridoped active carbon nanotubes (ACNTs) with abundant mesoporous structure enable fast Li+ transmittal and provide strong polysulfide adsorption ability. More importantly, they offer enough mechanical strength to support high sulfur loading (77 wt %) that maximizes their chemical role and can accommodate large volume changes. The N, B, S tridoped ACNTs/S composite exhibits a superb incipient capacity of 1166 mAh/g-S at 0.3 C and large reversible capacity of 881 mAh/g-S at the 700th cycle. To further promote the cyclic lifespan of LSB, the as-prepared N, B, S tridoped ACNTs acted as both sulfur matrix and spring functional layer and achieved a large reversible specific capacity of about 713 mAh/g-S at the 1400th cycle at lofty current density of 0.5 C with a slow capacity decay of 0.014% 1/cycle and a higher sulfur loading of 90 wt %. Accordingly, reasonable design for the heteroatom doping element in carbon material and separator modification will be distinctly vital for enhancing the electrochemical performance of the LSB and boosting its industrial application.