Intercalation pseudo-capacitance behavior of few-layered molybdenum sulfide in various electrolytes

The insertion and de-insertion of ions in layered materials are important processes during the energy storage. The investigation on the preparation and electrochemical properties of layered materials attracts a lot of attention. Here, few-layered MoS₂ nanosheets are prepared by solvothermally treating ammonium tetrathiomolybdate ((NH₄)₂MoS₄) in the presence of hydrazine and cetyltrimethylammonium bromide (CTAB). The structure and electrochemical properties of few-layered MoS₂ have been characterized and explored in detail. The results show that ions intercalation causes an interlayer spacing change of the obtained MoS₂, and that the prepared few-layered MoS₂ exhibits fairly good specific capacitance (330.8 F g^-1 at 2.0 A g^-1), a high rate capability (specific capacitance can still retain 256 F g^-1 at 40 A g^-1) and good cycle stability (capacitance can retain 88.8 % over 5000 cycles). Furthermore, different from most of the current literatures in which MoS₂'s capacitance is generally attributed to electric double-layer capacitance, the relationships between current responses and scan rates uncover that few-layered MoS₂'s capacitance mainly comes from intercalation pseudo capacitance. The result of this work predicts that few layered-MoS₂ can be developed as a promising electrode material for energy storage.