Exfoliated MoS2/C Composite As a High-Performance Anode for Sodium Ion Batteries

Molybdenum disulphide (MoS₂) has a graphite-like structure, where Mo and S atoms are covalently bonded to form two-dimensional S-Mo-S trilayers. It could be a desirable intercalation host material for sodium ions. We report on an exfoliated MoS₂/C composite (E-MoS₂/C) for SIBs with outstanding electrochemical properties, which possesses a unique grapheme-like structure (Figure 1a). Our strategy to achieve high performances is to use a unique E-MoS₂/C composite as an anode material that possesses expanded d-spacing to accommodate large sodium ions. In addition, the exfoliated structure could shorten the Na-ion diffusion pathway and also withstand large volume change due to the buffering space created by the crumpled nanolayers. Simultaneously, the carbon component can effectively increase electrode conductivity. As shown in Figure 1b, various electrolytes were utilized to optimize the cycling performance of E-MoS₂/C. The E-MoS₂/C is presented as an excellent anode material in 1.0 M NaClO₄ with propylene carbonate / ethylene carbonate and 5 wt % fluoroethylene carbonate additive (PC/EC + 5 wt % FEC), with an average working voltage of 1.0 V. Coupled with the average capacity of ~ 400 mAh g^-1 for 100 cycles at applied current of 100 mA g^-1 (0.25 C) and excellent rate capability (467.7 mAh g^-1 at 0.125 C and 290.1 mAh g^-1 at 5 C ), as well as high energy density of 400 Wh Kg^-1, this material could be a promising anode candidate for SIBs at room temperature.

Figure 1 SEM image (a) and cycling performances (b) of E-MoS₂/C at various electrolytes.