Enhanced performance of lithium sulfur batteries with conductive polymer modified separators

Abstract

The separators of Li–S batteries are modified with polypyrrole (PPy) nanotubes, PPy nanowires and reduced graphene oxide (rGO), respectively. All the conductive materials for the separator surface decoration can inhibit the migration of lithium polysulfides in the electrolyte and decrease the polarization of the sulfur cathode. Thus, the shuttle effect and redistribution of the active material can be suppressed during the charge/discharge process, resulting in enhanced performance. Moreover, the adsorption effect of PPy to lithium polysulfides is stronger compared to that of rGO, and the wettability of the PPy modified separators towards the electrolyte is much better, resulting in further enhanced electrochemical performance of Li–S batteries. Particularly, with approximately 2.5–3 mg cm⁻² sulfur loading, the Li–S battery using the PPy nanotube modified separator displays an initial discharge capacity of 1110.4 mA h g⁻¹, and a retained capacity of 801.6 mA h g⁻¹ after 300 cycles at 0.5C, demonstrating an average coulombic efficiency up to 90.6% in the LiNO₃-free electrolyte.