Core-shell FeS2@NSC grown on graphene for high performance lithium-ion storage

[Display omitted] •Small size FeS2 encapsulated by N, S co-doped carbon shells and distributed on S-doped graphene.•FeS2 was produced and S was successfully doped into the carbon skeleton by a one-step vulcanisation process.•The unique two-carbon encapsulated structure can greatly limit the volume expansion of FeS2 during charging and discharging.•The successful introduction of heteroatoms can cause more defects, which provides more reaction sites for electrochemical reactions and improves the rate of charge transfer. FeS2 is considered a promising anode candidate for LIBs (lithium-ion batteries) due to its low cost and high theoretical capacity. However, the large volume expansion and low conductivity of FeS2 limit its further applications. In this work, a novel FeS2-based materials with two-carbon encapsulated structure has been designed to solve the above problems. This unique structure is constructed of spindle-shaped FeS2 nanoparticles embedded in N/S co-doped carbon shell and covered by three-dimensional sulfur-doped graphene (FeS2@NSC/SG). The FeS2@NSC/SG composite shows excellent lithium storage performance benefiting from the unique two-carbon encapsulated structure. FeS2@NSC/SG electrode delivers a reversible capacity of 944.6 mAh·g−1 after 120 cycles at 0.1 A·g−1 when it is used as anode for LIBs. Even at 5 A·g−1, the capacity of FeS2@NSC/SG electrode remains 270.8 mAh·g−1 after 500 cycles. The excellent rate performance of FeS2@NSC/SG electrode is attributed to the electrochemical behavior dominated by the capacitive behavior and this strategy will provide new ideas for potential electrode materials.