Fluorine heteroatoms were introduced to increase the limited specific capacitances of electric double-layer capacitors (EDLCs), and the effects of the fluorine atoms were analyzed. To introduce the fluorine, a CF4 plasma treatment was used that introduced the fluorine atoms quickly. Among the fluorine functional groups in the F6-ACA framework, the semi-ionic C–F bonds induced rapid charge transfer and imparted pseudocapacitance. Consequently, we achieved a specific capacitance of 325.68 F/g for the F6-CA sample at 0.5 A/g. By analyzing the contributions of the electric double-layer capacitance and the pseudocapacitance, we determined that the contribution from the pseudocapacitance was 37.57%. A remarkable specific capacitance retention rate of 95.87% was obtained over 1000 charge/discharge cycles with a high current density of 3 A/g. Additionally, the semi-ionic C–F bonds reduced the charge transfer resistance ( Rct) by 36.8%. Therefore, the specific capacitance was improved by the fluorine heteroatoms, and the semi-ionic C–F bonds played a pivotal role in this improvement.

Effect of fluorine functional groups introduced into activated carbon aerogel by carbon tetrafluoride plasmas in supercapacitors
    Abstract
    1 Introduction
    2 Materials and methods
        2.1 Preparation of activated carbon aerogels
        2.2 Plasma fluorination
        2.3 Characterization
        2.4 Electrochemical analyses
    3 Results and discussion
        3.1 Characteristics of the ACA and F-ACA​
        3.2 Electrochemical performance
        3.3 Assessing the contributions of EDLC and PC
    4 Conclusion
    Acknowledgements 
    References

• Seongjae Myeong(Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea)
• Seongmin Ha(Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea)
• Chaehun Lim(Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea)
• Chung Gi Min(Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea)
• Young‑Seak Lee(Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea, Institute of Carbon Fusion Technology (InCFT), Chungnam National University, Daejeon 34134, Republic of Korea) Corresponding author