FeS@onion-like carbon nanocapsules embedded in amorphous carbon for the lithium ion batteries with excellent cycling stability

The development of lithium ion battery with long-term cycle stability is considered to be a prerequisite for commercialization. Onion-like carbon coated FeS nanocapsules embedded in amorphous carbon (FeS@OLC/a-C) is designed and one-step developed via discharging the Fe-C composite ingot under the atmosphere of Ar and H2S. In FeS@OLC/a-C nanocomposites, ~ 8.9 nm FeS@OLC nanocapsules with an average onion-like shell of 2 nm are covered by the amorphous carbon. The formation mechanism has been proposed for FeS@OLC/a-C nanocomposites. As the lithium ion battery anode candidate, FeS@OLC/a-C nanocomposite electrode have the advantages of good cycling stability (719.2 mAh g−1 after being cycled at 0.1 A g−1 for 200 times) and excellent high-rate performances (569.3 mAh g−1 for 2 A g−1, 540.9 mAh g−1 for 4 A g−1, 466.6 mAh g−1 for 8 A g−1 and 340.0 mAh g−1 for 16 A g−1), which originates from the combined effect of small FeS nanoparticles, the onion-like carbon layers and amorphous carbon. The design idea in this paper provides a new approach for improving the cycling stability and rate capability of lithium ion battery.