In this study, polyimide (PI)-based activated carbon fibers (ACFs) were prepared for application as electrode materials in electric double-layer capacitors by varying the steam activation time for the PI fiber prepared under identical cross-linking conditions. The surface morphology and microcrystal structural characteristics of the prepared PI-ACFs were observed by field-emission scanning electron microscopy and X-ray diffractometry, respectively. The textural properties (specific surface area, pore volume, and pore size distribution) of the ACFs were calculated using the Brunauer–Emmett–Teller, Barrett–Joyner–Halenda, and non-local density functional theory equations based on N2/ 77 K adsorption isotherm curve measurements. From the results, the specific surface area and total pore volume of PI-ACFs were determined to be 760–1550 m2/ g and 0.36–1.03 cm3/ g, respectively. It was confirmed that the specific surface area and total pore volume tended to continuously increase with the activation time. As for the electrochemical properties of PI-ACFs, the specific capacitance increased from 9.96 to 78.64 F/g owing to the developed specific surface area as the activation time increased.

Preparation of polyimide-based activated carbon fibers and their application as the electrode materials of electric double-layer capacitors
    Abstract
    1 Introduction
    2 Experiment
        2.1 Materials and curing
        2.2 Preparation of PI-based ACFs
        2.3 Characterization
        2.4 Electrochemical measurements
    3 Results and discussion
        3.1 Morphology analysis
        3.2 Microstructural and textural properties
        3.3 Electrochemical characterization
    4 Conclusions
    References

• Da‑Jung Kang(Material Application Research Institute, Jeonju University, Jeonju 55069, Republic of Korea)
• Hye‑Min Lee(Convergence Research Division, Korea Carbon Industry Promotion Agency, Jeonju 54853, Republic of Korea)
• Kay‑Hyeok An(Material Application Research Institute, Jeonju University, Jeonju 55069, Republic of Korea, Department of Advanced Materials and Chemical Engineering, Jeonju University, Jeonju 55069, Republic of Korea)
• Byung‑Joo Kim(Material Application Research Institute, Jeonju University, Jeonju 55069, Republic of Korea, Department of Advanced Materials and Chemical Engineering, Jeonju University, Jeonju 55069, Republic of Korea) Corresponding author