MoS₂ Hollow Multishelled Nanospheres Doped Fe Single Atoms Capable of Fast Phase Transformation for Fast-charging Na-ion Batteries

Low Na⁺ and electron diffusion kinetics severely restrain the rate capability of MoS₂ as anode for sodium-ion batteries (SIBs). Slow phase transitions between 2H and 1T, and from Na_xMoS₂ to Mo and Na₂S as well as the volume change during cycling, induce a poor cycling stability. Herein, an original Fe single atom doped MoS₂ hollow multishelled structure (HoMS) is designed for the first time to address the above challenges. The Fe single atom in MoS₂ promotes the electron transfer, companying with shortened charge diffusion path from unique HoMS, thereby achieving excellent rate capability. The strong adsorption with Na⁺ and self-catalysis of Fe single atom facilitates the reversible conversion between 2H and 1T, and from Na_xMoS₂ to Mo and Na₂S. Moreover, the buffering effect of HoMS on volume change during cycling improves the cyclic stability. Consequently, the Fe single atom doped MoS₂ quadruple-shelled sphere exhibits a high specific capacity of 213.3 mAh g^-1 at an ultrahigh current density of 30 A g^-1, which is superior to previously-reported results. Even at 5 A g^-1, 259.4 mAh g^-1 (83.68 %) was reserved after 500 cycles. Such elaborate catalytic site decorated HoMS is also promising to realize other "fast-charging" high-energy-density rechargeable batteries.