Hefei Institute of Material Science in the development of ultra-high energy storage density supercapacitors
Recently, Wang Zhenyang, a researcher at the Institute of Solid State Physics, Hefei Institute of Material Science, Chinese Academy of Sciences, achieved large-scale preparation of macro-thick graphene crystal films, and made progress in the development of ultra-high energy storage density supercapacitors. The researchers used the laser-induced processing method to directly convert the polyimide precursor into a graphene crystal film in situ; in view of the technical bottleneck of the volume effect when it is directly used as an energy storage electrode, by optimizing the molecular configuration of the precursor And thermal sensitivity, which greatly increases the depth of action between the laser and the polymer film, and thus realizes the preparation of the macroscopic thickness of the porous graphene crystal film; the supercapacitor constructed as an electrode has significant energy storage density and cycle stability Promote. The related results were published in Journal of Power Sources under the title of Ultra-thick 3D graphene frameworks with hierarchical pores for high-performance flexible micro-supercapacitors.
Graphene has a series of advantages such as large specific surface area, good electrical conductivity, and high stability. It has been widely studied in recent years and used as an electrode material for supercapacitor energy storage devices. The excellent electrochemical performance of graphene electrodes under microscopic size has been extensively studied and confirmed. However, the large-scale application of graphene supercapacitors requires the preparation and assembly of electrodes on the macro-scale (large area and ultra-high thickness) on the premise of maintaining their excellent electrochemical performance. However, in a graphene electrode with a macroscopic thickness, ion diffusion is usually limited, and the stacking of graphene sheets will also cause a large internal resistance, resulting in a decrease in electrochemical performance. Therefore, how to design and prepare electrode materials with both macroscopic thickness and rich pore structure is an urgent problem in the industrial application of graphene supercapacitors.
To this end, the researchers used a fast, efficient, simple, environment-friendly, and synchronously patterned high-energy laser induction method to prepare in situ three-dimensional porous graphene crystal films on a polyimide substrate. In order to control the interaction between the laser and the polyimide precursor, the researchers adjusted the degree of imidization and molecular configuration of the product polyimide by controlling the stoichiometric ratio of the raw materials and the imidization reaction temperature, thereby changing its Thermal sensitivity. Finally, a hierarchical porous structure graphene crystal film with a thickness of up to 320 μm was grown on the polyimide film in situ, with an area and volume specific capacitance as high as 172.2 mF/cm2 and 4.13 mF/cm3, showing great application potential. Further in-situ electrodeposition of the pseudocapacitance material polypyrrole can produce a graphene/polypyrrole composite electrode with an area specific capacitance as high as 2412.2 mF/cm2. The study found that the planar interdigital flexible full-solid micro-state supercapacitor manufactured by using the composite electrode material as the electrode can obtain energy density and power density as high as 134.4 μWh/cm2 and 325.2 μW/cm2, and at the same time has excellent magnification. Performance, cycle stability and mechanical flexibility.
The above-mentioned work has been funded by several projects including the National Natural Science Foundation of China Joint Fund Project and Youth Fund Project.
Figure 1. Thermal sensitivity control of polyimide and laser-induced growth of macro-thickness graphene crystal film
Figure 2. The structure characterization of the macro-thickness graphene crystal film
Figure 3. Supercapacitor performance of graphene/polypyrrole composite
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