Lithium-ion batteries (LIBs) have intensely pervaded our daily life activities and evolved into the rampant power sources since its first launch in 1991 for various applications such as mobile phones, portable laptops, electric vehicles and energy storage systems due to their high energy density and excellent cycling stability.¹ Nevertheless, by considering the drawbacks of LIBs such as limited lithium resource over the earth’s crust and the presence of uneven distribution of Li deposites and thereby increasing cost will be the primary problem for the development of advanced energy storage system in the future. Sodium-ion batteries (SIBs) have attracted great attention due to the fact that Na⁺ ions have similar electrochemical properties with the Li⁺ ions, thus the available design of LIBs could have been promptly relocated to and hasten the research on SIBs. SIBs face the challenges in development of suitable anodes due to the large volume change during sodiation/de-sodiation resulting in inferior cycling stability. Being ecofriendly and copious, pyrrhotite (Fe_1-xS), has been considered as a potential anode material for SIBs.² However, the rapid capacity loss originated by the substantial volume expansion during electrochemical reaction hinders its practical applications. In this work, we present the design and synthesis of Fe_1-xS@N-doped carbon yolk-shell architecture as a promising anode material for SIBs. The optimized core-void-shell architecture exhibits the excellent capacity retention and high rate capability when compared to pristine pyrrhotite. The large electrode/electrolyte contact area and the short diffusion path for electrons and sodium ions which facilitated by the yolk-shell configuration lead to the enhanced sodium reaction rate and also mitigates the structural degradation.

References

1. G. Yang, J.L. Zhang, M.C.W. Kinter-Meyer, C.X. Lu, D.W. Choi, J.P. Lemmon and J. Liu, Chem. Rev., 111, 3577 (2011).
2. X. Wang, J. Yang, S.L. Chou, H.K. Liu, W.X. Zhang, D. Zhao and S.X. Dou, Nat. Commun., 6, 8689 (2015).