The Preparation Of Three Dimensional MoO₂@MoS₂/GO And NiO@NiS/GO And The Study On The Properties Of Supercapacitor

As a new type of energy storage equipment, the supercapacitor has the characteristics of fast charging and discharging, long service life and high power density. Electrode material is one of the key factors for the performance of the super capacitor. Carbon material is becoming the focus of attention due to its large surface area and low price in recent years. Among of them, graphite foam is a kind of three dimensional porous material, which with a large surface area, low density, high porosity ratio and high conductivity. Transition metal oxides with various valences, when they are used as electrode materials they will storage energy with static charge, the electrolyte ions and metal oxides will occure oxidation reduction reaction to produce Faraday pseudo capacitance. In this paper, three dimensional graphite foam is used as the basic framework, and it can load metal oxide nanoparticles on its surface. They can have the synergistic effect between each other, the metal oxide adhered on the surface of graphene sheets, which can reduce the aggregation between sheets and increase the specific surface area of graphene at the same time. Graphite sheet also contributes to the formation of metal oxide nanostructures, and can control the dispersion of metal oxides. Three dimensional structure inhibition the deformation between graphite sheets and the reunion of particle volume. The prepared three dimensional composite materials of supercapacitors were as the next research object. Metal oxide loaded on the graphite foam would changed to stable metal sulfide through the ion exchange. The stability of the use of sulfide can improve the stability of the electrode material during the charging and discharging process.The preparation of three dimensional MoO₂@MoS₂/GO and the study on the properties of supercapacitor. The 3D MoO₂/GO composite materials were prepared by hydrothermal method and chemical bath method respectively. they both have a high specific capacitance. However, the composite materials prepared by hydrothermal method have larger specific capacitance, such as, at the current density of 2 A·g-1, the capacitance of the two kinds of materials are 523.8 F·g-1 and 416.8 F·g-1 respectively. The composite prepared by hydrothermal method has a excellent uniform and dispersion, and the capacitance of the composite is 200.9 F·g-1 at 10 A·g-1. In addition, capacity can be maintained 60.3% after charging and discharging 1000 times. The result fully demonstrated the high capacity and high magnification of the three dimensional graphite foam. Aiming at the problem about the stability of MoO₂ in aqueous solution is not ideal, the external MoO₂ was changed to MoS₂ by the ion exchange method to improve the stability of the whole electrode materials in the aqueous electrolyte system. For example, the capacity retention rate of the electrode material increased from 60.3 % to 81.4 % after 1000 cycles of charging and discharging.The preparation of three dimensional NiO@NiS/GO and the study on the properties of supercapacitor. The 3D NiO/GO composite materials were prepared by hydrothermal method and chemical bath method. we found that the composite materials prepared by hydrothermal used as the electrode material of the supercapacitor had a higher capacitance and stability. For example, when the current density is 10 A·g-1, the capacitance of the two methods is 3186.2 F·g-1and 2560.7 F·g-1, respectively. The composite prepared by hydrothermal method has a larger specific surface area, which is beneficial to increase the contact surface between the electrode material and the electrolyte. When the current density is 18 A·g-1, the capacitance is still up to 1200.6 F·g-1. In addition, when the current density is 15 A·g-1, the capacity retention rate is 52.1% after 1000 cycles of charging and discharging. Partial NiO can be exchanged into the stable NiS through the ion exchange method. The results show tthe capacity retention rate is improved from 52.1 % to 66.9 % after ion exchange.