Unraveling the Na-ion storage performance of a vertically aligned interlayer-expanded two-dimensional MoS2@C@MoS2 heterostructure

Abstract

Achieving hierarchically uniform surface manipulated nanostructured materials is important to accomplish high performance storage devices, but it is still challenging. Herein, we successfully synthesized a vertically-aligned interlayer-expanded caterpillar-like heterostructure consisting of MoS₂@C nanosheets (NSs) over MoS₂ nanorods (NRs) (MoS₂@C@MoS₂) as an advanced anode material for sodium-ion batteries (SIBs). Step-wise ramp rate tuned MoS₂ nanorods (NRs) were achieved via surface sulfurization of MoO₃ NRs by a vapor phase ion-exchange method. Heterointerphased MoS₂@C nanosheets performed a crucial role in enacting an excellent electrochemical performance by facilitating better Na⁺ ion diffusion and faster electron transport. The hierarchical MoS₂@C@MoS₂ electrode delivered a high specific capacity of 434 mA h g⁻¹ (after 100 cycles at 100 mA g⁻¹) and excellent cycling stability (352 mA h g⁻¹ after 200 cycles at 1000 mA g⁻¹). Kinetic analysis revealed that an enhanced sodium storage performance of the MoS₂@C@MoS₂ electrode could be accompanied by an ameliorated capacitive contribution reaction. Moreover, the sodium-ion full cell assembled with the MoS₂@C@MoS₂ anode and a Na₃V₂(PO₄)₂F₃ cathode exhibited a high specific capacity of 320 mA h g⁻¹ with good capacity retention.