Ma Yanwei, Research Institute of Electrical Engineering, Chinese Academy of Sciences, made progress in the quantitative preparation of graphene and high performance graphene-based supercapacitors . He proposed the use of carbon dioxide as raw material and self-propagating high-temperature synthesis technology to achieve high conductivity and high specific surface area. Fast, green, and low-cost preparation of graphene powder. The relevant research results have been published in the international journal Advanced Materials (2017, 1604690) and applied for national invention patents and PCT patents.
figure 1. Schematic diagram of self-propagating high-temperature synthesis of graphene
Graphene is a new type of material that has received much attention in recent years, but the industrial large-scale preparation of high-quality graphene has been a worldwide problem. At present, the technical route for the scale-up preparation of graphene powder is mainly based on the expanded graphite stripping method and the graphite oxide reduction method, but the former usually obtains a multilayer graphite sheet having a low specific surface area, and the graphene prepared by the latter has a residual oxygen function. Group and structural defects lead to low conductivity, which severely limits the potential applications of graphene.
In response to the above problems, the team used carbon dioxide as a raw material, magnesium metal powder as a reducing agent, and nanometer magnesium oxide as a template. Through the self-propagating combustion method of magnesium powder in a carbon dioxide atmosphere, a graphene rich in mesoporous structure was successfully prepared, such as Figure 1 shows. The graphene has a conductivity of up to 13,000 S/m and a specific surface area of ​​709 m2/g. It has excellent comprehensive properties and exhibits superior electrochemical performance in ionic liquid electrolytes. Based on the specific capacitance of the electrode material up to 244 F / g, energy density up to 136 Wh / kg, power density up to 1000 kW / kg, after 1 million cycles, the capacity retention rate is still greater than 90%, as shown in Figure 2. The graphene preparation method has a short reaction time, is environmentally friendly, has low cost, and is easy to be industrialized, and will effectively promote the practical application of graphene in energy storage fields such as supercapacitors .
The research was completed in cooperation with the Li Jiangtao research team of the Institute of Physics and Chemistry of the Chinese Academy of Sciences and the Li Jianqi research team of the Institute of Physics of the Chinese Academy of Sciences, and was funded by the National Natural Science Foundation of China.
figure 2. Energy/power performance and cycle life of graphene-based supercapacitors
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