In this study, nitrogen and fluorine co-doped carbon nanocages (NF-CNCs) were synthesized as anode materials for potassium- ion batteries (KIBs), and their structural evolution with heat treatment and electrochemical behavior with different functional groups was investigated. NF-CNCs were prepared by physically mixing coal tar pitch (CTP) with a SiO2 template, followed by heat treatment and subsequent fluorination with NF3 gas. A systematic investigation of the structural properties revealed that graphitization increased with increasing heat treatment temperature as the carbon structure transitioned from amorphous at 500 and 1000 °C to graphite-like at 1500 °C. Furthermore, nitrogen and fluorine functional group analysis revealed significant changes, particularly in terms of covalent and semi-ionic C‒F bonds. Among the samples, NF-CNC 1000 displayed excellent electrochemical performance, with a specific capacity of 395.1 mAh g− 1 and a capacity retention rate of 94% during 1000 cycles at 50 mA g− 1. The exceptional performance of NF-CNC 1000 is attributed to its high porosity, amorphous carbon structure, and semi-ionic C‒F bonds, which facilitate the efficient adsorption and intercalation of potassium ions. These findings provide valuable insights into the design of advanced anode materials for next-generation KIBs.

NF co-doped carbon nanocages engineered with NF3 fluorination for use in highly stable potassium-ion batteries
    Abstract
        Graphical abstract
    1 Introduction
    2 Experimental section
        2.1 Preparation of the NF-CNCs
        2.2 Characterization of the NF-CNCs
        2.3 Electrochemical measurements
    3 Results and discussion
    4 Conclusion
    Acknowledgements 
    References

• 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)
• Seongjae Myeong(Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea)
• Seoyeong Cheon(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
• Go Bong Choi(Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), National Creative Research Initiative Center)