Embedding FeS nanodots into carbon nanosheets to improve the electrochemical performance of anode in potassium ion batteries

Potassium-ion batteries (PIBs) is one of the most promising alternatives for Lithium-ion batteries (LIBs) due to the low-cost and abundant potassium reserves. However, the electrochemical performances of PIBs were seriously hindered by the larger radius of potassium ions, resulting in a slow kinetic during the electrochemical reaction, especially in the PIB anodes. In the study, we propose FeS nanodots embedded S-doped porous carbon ([email protected]) synthesized by a simple self-template method for the storage of potassium-ions. The FeS nanodots with an average diameter of 5 nm are uniformly distributed in S-doped porous carbon nanosheets. When the [email protected] was used as the anode in PIBs, the unique structure of [email protected] can relieve the agglomeration and volume expansion of FeS effectively during the charge–discharge process. Even after 3000 cycles, the FeS nanodots are still uniformly embedded in porous carbon without agglomeration. Ascribed to the merits, the [email protected] exhibits a reversible capacity of 309 mAh g−1 at 0.1 A g−1 after 100 cycles and 232 mAh g−1 at 1 A g−1 after 3000 cycles. The excellent electrochemical performance of [email protected] is attributed to the synergistic effects of FeS nanodots and S-doped porous carbon, which facilitated the diffusion of electrolyte and accelerated the migration of potassium ions. Moreover, theoretical calculation results also suggest that the van der waals heterostructure of [email protected] displays higher adsorption energy for potassium ions than that of S-doped graphene, indicating the suitability of [email protected] for K storage.