The Application Of MoS₂ With Different Morphologies And MoS₂ Composite Materials In Supercapacitor

As a new kind of energy storage device, the supercapacitor has higher energy density and specific capacitance than conventional capacitors, and higher power density than batteries. Besides, it causes less pollution. Therefore, supercapacitor has broad application prospects. Molybdenum disulfide（MoS₂） is a typical metal sulfide, which has higher intrinsic ionic conductivity than oxide and higher theoretical specific capacitance than graphite. Also, this material has graphene-like layered structure. Therefore, it has attracted a lot of attention from scientists and been broadly used in capacitor electrode materials. This work adopts the hydrothermal method to synthesize different morphologies MoS₂,which are then used for supercapacitor electrode materials. The impacts of different morphologies upon electrochemical properties will be discussed in this work. In addition, MoS₂ and carbon composite materials were synthesized by hydrothermal method so as to overcome the deficiency of the homogeneous material and play a synergistic role, and their electrochemical properties were discussed in this work. The main contents include the following aspects:1. Different morphologies MoS₂ are synthesized by hydrothermal method under different experiment conditions, such as sulfur sources, molybdenum sources, reaction temperature, reaction time, and other conditions. And then these different morphologies MoS₂ were used in supercapacitor electrode material. The results show that hollow net MoS₂ has higher capacitance and energy density than that of three-dimensional flower-shaped MoS₂, hollow spherical MoS₂ and flocculent MoS₂. Three-dimensional flower-shaped MoS₂ and the hollow net MoS₂ as a supercapacitor electrode material have good electrochemical capacitance performance. They have higher energy density under high power density. And their specific capacitances reach up to 203 F/g, 259 F/g at current density of 1 A/g in 1 M Na2SO4 electrolyte, respectively.2. The tests of CV curves of different morphologies MoS₂ show that there are no redox peak with different scan rates, and their shapes are approximate to rectangle. Their GCD curves under different current densities are approximate to isosceles triangle. These indicate that the capacity of MoS₂ electrode material is completely provided by an electric double layer capacitor. The curves of forward and reverse scanning have shown the good symmetry, which indicates these electrode materials have good reversibility.3. The graphene oxide（GO） is synthesized by an improved Hummers method. MoS₂/RGO composite electrode material formed with GO and MoS₂, and its electrochemical properties were investigated. The results show that MoS₂/RGO composites as a supercapacitor electrode material has good electrochemical capacitance performance, and its specific capacitance reaches up to 376F/g、250F/g、201F/g、189F/g、168F/g at current density of 1、2、4、5、10A/g in 1 M Na2SO4 electrolyte, respectively. In particular, its specific capacitance reaches up to 168F/g at current density of 10A/g, which is much higher than that of hollow net MoS₂（99F/g）. Besides, the specific capacitance and energy density of MoS₂/RGO composites is significantly higher than that of the hollow net MoS₂.4. MoS₂/CNTs composite is synthesized by hydrothermal method. Cyclic voltammetry test indicates that the CV curve of MoS₂/CNTs composite shows that there is no obvious redox peak at different scanning rates, which indicates that the capacity of the electrode material is provided by the electric double layer capacitor. In addition, the presence of carbon nanotubes makes the potential window larger. The specific capacitance of MoS₂/CNTs composite reaches up to 264F/g、216F/g、172F/g、154F/g、108F/g at current density of 1、2、4、5、10A/g in 1 M Na2SO4 electrolyte, respectively.At same current density, its specific capacitance is slightly larger than that of the hollow net MoS₂.