With the increasing demand for flexible electronic devices, smaller and lighter flexible supercapacitors have gained significant research attention. Among the various materials, self-supporting reduced graphene oxide (rGO) paper has emerged as one of the most promising electrode materials for supercapacitors due to its low cost, high chemical/thermal stability, and excellent electrical conductivity. Nevertheless, a major drawback of rGO paper is the limited ion diffusion between stacked rGO layers, hindering the effective formation of electrochemical double-layer at the electrode/electrolyte interface. In this study, we prepared the rGO paper derived from ball-milled followed-by water oxidation process for reducing the sheet size. The smaller-sized rGO sheets facilitated ion transport between graphene layers, promoting efficient electric double-layer formation. Moreover, the increased presence of edge planes in ball-milled rGO sheets achieved high capacitance, further enhancing the performance of rGO as an electrode material. Notably, the 2-BMOX rGO paper obtained from ball-milling and wet-oxidized graphite exhibited a capacitance of 117.9 F/g in cyclic voltammetry (CV) and 128.6 F/g in galvanostatic charge–discharge (GCD) tests, approximately twice that of conventional rGO. Additionally, the capacitance retained 91% of its initial performance after 2,000 cycles, indicating excellent cycling stability.

Water-oxidized and ball-milled reduced graphene oxide based self-supporting electrodes for high performance flexible supercapacitors
    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials
        2.2 Synthesis of BMOX GO
        2.3 Fabrication of BMOX rGO paper
        2.4 Fabrication of rGO paper cell
        2.5 Characterization
        2.6 Electrochemical measurements
    3 Results and discussion
        3.1 Physical properties of x-BM, x-BMOX carbons (graphite, GO, and rGO)
        3.2 Electrochemical characterization of x-BMOX carbons (GO, and rGO)
    4 Conclusion
    Acknowledgements 
    References

• Jae Young Jung(Hydrogen Research and Demonstration Center, Hydrogen Energy Institute, Korea Institute of Energy Research (KIER), Jeollabuk‑Do, Buan 56332, Republic of Korea)
• Dong‑gun Kim(School of Chemical Engineering, School of Semiconductor and Chemical Engineering, Clean Energy Research Center, Jeonbuk National University, Jeonju 54896, Republic of Korea)
• Sungkwon Jung(School of Chemical Engineering, School of Semiconductor and Chemical Engineering, Clean Energy Research Center, Jeonbuk National University, Jeonju 54896, Republic of Korea)
• Sujin Kim(School of Chemical Engineering, School of Semiconductor and Chemical Engineering, Clean Energy Research Center, Jeonbuk National University, Jeonju 54896, Republic of Korea)
• Jae‑yeong Kang(School of Chemical Engineering, School of Semiconductor and Chemical Engineering, Clean Energy Research Center, Jeonbuk National University, Jeonju 54896, Republic of Korea)
• Yong‑seong Park(School of Chemical Engineering, School of Semiconductor and Chemical Engineering, Clean Energy Research Center, Jeonbuk National University, Jeonju 54896, Republic of Korea)
• Pil Kim(School of Chemical Engineering, School of Semiconductor and Chemical Engineering, Clean Energy Research Center, Jeonbuk National University, Jeonju 54896, Republic of Korea)
• Nam Dong Kim(Functional Composite Materials Research Center, Korea Institute of Science and Technology (KIST), Jeollabuk‑Do, Wanju 55324, Republic of Korea) Corresponding author
• Hongbum Kim(Functional Composite Materials Research Center, Korea Institute of Science and Technology (KIST), Jeollabuk‑Do, Wanju 55324, Republic of Korea, Department of Applied Bioengineering, Graduate School of Convergence Science and Technology, Seoul National University, Gyeonggi‑Do, Suwon 16229, Republic of Korea)