Grape-cluster-like hierarchical structure of FeS2 encapsulated in graphitic carbon as cathode material for high-rate lithium batteries

A unique grape-cluster-like hierarchical structure in which FeS2 is encapsulated in graphitic carbon (FeS2@GC) composite has been elaborately designed to address the limitations in rechargeable Li-FeS2 batteries, such as poor electronic/ionic conductivity, dissolved polysulfide intermediates, and large volume changes. In particular, the individual grape grain of FeS2@GC particle with a yolk-shell structure that graphitic carbon shell and FeS2 nanoparticle core can significantly enhance the electrical conductivity, buffer volume changes, and confine the generated polysulfide intermediates. Thus, these high-efficiency individuals as the reaction units can facilitate the electrochemical redox reactions, improving the reaction kinetics. In addition, the closely connected individual FeS2@GC particles can construct a grape cluster to further enhance the electrical conductivity, facilitating ion/electron transport in the electrode. Consequently, the FeS2@GC composite demonstrates excellent electrochemical and stable cycling performances, particularly at high C-rates. A reversible capacity of 661 mAh g−1 after 200 cycles at 1 C, corresponding to a capacity retention of 97.5% of 2nd cycle (678 mAh g−1), and a capacity decay rate of 0.012% per cycle are achieved. Even at a higher rate of 10 C, a high capacity retention of 407 mAh g−1 after 1000 cycles is maintained, which indicates excellent cycling stability and superior rate capability.