Facile synthesis of graphitized carbon nanosheets from Chlorella with multiple Fe active sites to modify separator for efficient Li-S batteries

Abstract

Li-S battery as an alternative to next-generation battery systems suffers from electrical insulating properties of sulfur, “shuttle effects” and slow kinetics of lithium polysulfides (LiPSs). Separator modification via catalysts with multiple scales of active sites are great potential; however, the preparation of such a kind of catalysts is still complex and tedious. Here, we developed a facile pyrolysis strategy to fabricate multiple Fe active sites on N-doped porous graphitized carbon nanosheets (Fe-NG) from Chlorella, including atomically dispersed Fe single atoms, Fe nanoclusters and carbon-coated Fe nanoparticles, which enhanced the affinity to LiPSs and accelerated their conversion kinetics. As Fe-NG was utilized to modify the separators, the resulting Li-S battery demonstrated an initial discharge capacity of 1062.1 mAh g−1 at 1 C and maintained at 678 mAh g−1 after 500 cycles with the average capacity decay rate of 0.072 % per cycle. This work provides a rational design and large-scale preparation routes for separator modifying catalysts with heterogeneous active species on biomass-derived carbons.