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 (FeS@SPC) 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 FeS@SPC was used as the anode in PIBs, the unique structure of FeS@SPC 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 FeS@SPC 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 FeS@SPC 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 FeS@SPC displays higher adsorption energy for potassium ions than that of S-doped graphene, indicating the suitability of FeS@SPC for K storage.