Study on the transformative characteristics of mesophase asphalt formation and the electrochemical performance of its derived porous carbon

In this paper, the transformation characteristics of coal tar asphalt with different structures (Medium-temperature asphalt (MCTP), High-temperature asphalt (HCTP), Coal liquefaction asphalt (CLP), and Refined asphalt (RCTP)) in the mesophase state were investigated, and the electrochemical performance of mesophase asphalt-based porous carbon was analyzed. The results show that the mesophase asphalt has a higher aromatic carbon ratio and lower aliphatic carbon ratio than the raw asphalt. CLP has the lowest aromaticity (f ar  = 68.25 %), which is easy to condense but weak in reactivity. Although the aromaticity of MCTP is higher than that of CLP, its light component content is high and difficult to condense. Therefore, MCTP mesophase asphalt (MCTP-MP) has a larger interlayer spacing than CLP mesophase asphalt (CLP-MP). HCTP has abundant solid carbon and aromaticity, and the carbon layer structure of HCTP mesophase asphalt (HCTP-MP) tends to be more disordered (I D /I G  = 0.6). RCTP has better condensation degree and suitable lightweight components (9.75 %) than other asphalts. This makes RCTP mesophase asphalt (RCTP-MP) have higher graphitization degree (I D /I G  = 0.31) and good reactivity, and its derived porous carbon (RCTP-MPH) layer structure is efficiently stacked, which is more conducive to charge transport. The specific capacitance of RCTP-MPH is as high as 331F/g (0.5 A/g), and the power density of the RCTP-MPH electrode material is as high as 31.43 Wh/kg at a power density of 198.13 W/kg. After 10,000 cycles (5 A/g), the coulombic efficiency of the RCTP-MPH electrode material can reach 92.99 %.