A polypyrrole-supported carbon paper acting as a polysulfide trap for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries with high theoretical capacities and low cost are a strong candidate for future energy storage, but their development is hindered by many shortcomings, such as high-rate capacity decay due to the "shuttle effect". Herein, we increase the capacity retention and cycle life of the Li-S battery through the addition of an interlayer made of polypyrrole (PPy)-treated carbon paper (CP) in a Li-S battery. We first quantitatively investigate the effect of the thickness of the carbon paper and then optimize a novel interlayer prepared by using PPy adhered to the carbon paper. The results show that 300 μm CP is the best choice among the three thicknesses. The CP-300 samples deliver a reversible capacity of 490 mAh g^-1 after 200 cycles with a 0.5 C rate and show the best rate performance. Because of the porous structure and conductivity of the as-prepared PPy interlayer, the battery incorporating the PPy interlayer exhibits more excellent cycle performance and better rate performance than the CP batteries. Surprisingly, the PPy-coated CP-200 battery displays a reversible capacity of 555 mAh g^-1 after 200 cycles with a 0.5 C rate. This feasible way to modify a carbon paper interlayer may have promising prospects in the Li-S battery field.