A rGO-CNT aerogel covalently bonded with a nitrogen-rich polymer as a polysulfide adsorptive cathode for high sulfur loading lithium sulfur batteries

摘要

The development of high capacity lithium-sulfur (Li-S) batteries is hampered by both the shuttle effect of polysulfides and low sulfur areal loading problems. To inhibit the shuttle effect, a polysulfide adsorptive polymer polyethylenimine (PEI) is covalently bonded with reduced graphene oxide (rGO) in a one-step hydrothermal reaction. Meanwhile, multi-walled carbon nanotubes (MWCNTs) are simultaneously interweaved with rGO. The resultant PEI-rGO-MWCNT aerogel (PEI-GC) provides ample chemisorption domains of amine groups and abundant electrical contact sites. Density functional theory (DFT) calculations prove a binding energy of 2.43 eV between PEI and polysulfide. The PEI-GC cell achieved a high capacity of 933 mA h g(-1) for the 500th cycle at 1C, stable rate performance up to 10C, and low self-discharge rate. The covalent bond between PEI and rGO experiences no degradation during the 500 cycles. Moreover, PEI-GC achieved excellent cycling performance at a high sulfur loading of up to 18 mg cm(-2).