Layered iron dichalcogenides with high ion mobility and capacity as promising anode materials for alkali metal-ion batteries: A first-principles study

Developing high-performance anode materials remains a key challenge for alkali metal-ion batteries (AIBs). Benefiting from a high surface-to-bulk ratio, layered materials are promising candidates for anodes due to their potential high specific capacity and low ion transport resistance derived from the numerous ion storage sites and inherent open channels. In this work, we predict that the recently synthesized layered iron dichalcogenides, namely FeX2 (X = S, Se, Te), are suitable anode materials for AIBs through first-principles calculations. The results show that both the pristine and alkali-metalized FeX2 monolayers are structurally stable and present a metallic nature. In addition, the alkali metal-ions exhibit low diffusion barriers (0.15 eV for Li-ions, 0.08 eV for Na-ions, and 0.05 eV for K-ions) on FeX2 monolayers, which indicates that they possess a high ionic conductivity as well as an excellent rate capability and cycling performance. Besides, the calculated low open-circuit voltage values (0.39, 0.29, and 0.19 V vs. Na/Na+ for FeS2, FeSe2, and FeTe2, respectively) reveal that layered FeX2 materials are suitable to serve as anodes for sodium-ion batteries (SIBs). As a result, FeS2 and FeSe2 monolayers exhibit a high theoretical specific capacity (893.6 and 501.4 mAh g-1, respectively) for SIBs, while the theoretical volume-specific capacity of FeTe2 monolayer (2343.3 mAh cm-3) is around two times larger than that of standard commercial cells. Our findings suggest that these currently unexploited layered iron dichalcogenides could be potential high-performance anode materials for AIBs.