The coking industry produces a large number of low-value coal asphalt by-products. How to make it high-value-added has always been the focus of attention. The porous electrode carbon prepared with its low ash content and high carbon residue characteristics can be used for electrochemical energy storage, etc. Emerging energy field. However, the coal tar pitch needs to undergo liquid phase carbonization during the high-temperature carbonization process, so it is extremely difficult to control its microscopic morphology and pore structure. In addition, the reactive inertness of the fused ring molecules makes the surface chemical properties of the carbon products difficult to tailor.
In recent years, Li Kaixi, a researcher of the 702 research group of the Institute of Coal Chemistry, Chinese Academy of Sciences, and the scientific research team led by them have constructed a series of nano-structured electrode materials without template using precise design of asphalt molecules (Figure 1), and assembled high-performance flexible Solid capacitors and asymmetric capacitors have achieved significant improvements in their energy density and cyclic stability, and the cross-linking self-assembly strategy has also been successfully applied to the asphalt-based spherical activated carbon production line, achieving both basic and application breakthroughs.
The refined understanding of coal asphalt composition is a prerequisite for its efficient use. By constructing a suitable solvent system, it is cut into groups with similar composition structures. According to the molecular characteristics of the quinoline soluble components in the asphalt, the After chemical modification and conventional activation, nano-layered carbon for all-solid-state supercapacitor applications was constructed (Journal of Materials Chemistry A, 2017, 5 (30); Fuel, 2019, 242: 184-194). Subsequently, based on the principle of self-foaming of light-weight components, the honeycomb porous carbon morphology and mesopore ratio were adjusted to significantly increase the internal electrolyte mass transfer and surface interface active site exposure (ACS Sustainable Chemistry & Engineering, 2018 , 7 (2): 2116-2126). In order to precisely control the spacing of fused ring molecules, a large number of dangling bonds are grafted by means of oxidative cross-linking, which is used as a "handle" to promote the controlled self-assembly of molecules to achieve the nano-layered carbon micro-morphology and pore structure of 2-5 nm The synchronous control of the system further improves its electrochemical energy storage properties (Journal of Power Sources, 2019: 227446). In view of the directional design and optimization of surface chemical properties, which can effectively improve the electronic properties and chemical properties of carbon materials (ACS Applied Materials & Interfaces, 2019, 11 (14): 13214-13224), the free radical induces the polymerization of asphalt molecules and the carbon skeleton structure Doped with heteroatoms, N / S functionalized stacked carbon nanosheets were prepared (Figure 2). The assembled asymmetric all-solid supercapacitor has a specific capacitance of 458 F g-1 at a current density of 1A g-1, its volume energy density can reach 27 Wh L-1, and its power density is 296 W L-1 at 20,000 times. The capacity attenuation rate after cycling is only 5.9% (Figure 3), which is very suitable for narrow space application scenarios (Energy Storage Materials, 2020, 26: 119-128).
The construction strategy of coal pitch-based nanoporous carbon materials proposed in the above work has opened up new horizons for exploring the low-cost preparation of large-scale electrochemical energy storage electrode materials, and has obtained the National Natural Science-Shanxi Province Low Carbon Joint Key Fund Supported by the Provincial Natural Science Foundation and Shanxi Coal-based Key Scientific and Technological Research Projects.
Figure 1 Schematic diagram of preparing high-performance capacitor carbon from coal pitch
Figure 2 The micro-morphology and XPS and mapping analysis of the layered nano-carbon material
Figure 3 Characterization of electrochemical performance
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