This paper reports an enhanced strategy for improving the mechanical flexibility and ionic kinetic properties of a double network hydrogel based on Co2+- coordination assistance. The modified double-network hydrogel was obtained by using acrylic acid and N, N-dimethylacrylamide as monomers, adding cross-linking agents and 3D nitrogen-doped graphenes. The tensile fracture rate of the modified hydrogel was 1925% and its tensile strength was 1696 kPa. In addition, the hydrogel exhibited excellent ionic dynamics, and its application to an all-solid-state supercapacitor was able to achieve a specific capacitance of up to 182.8 F g− 1. The supercapacitor exhibited an energy density of 34.2 Wh kg− 1, even when operating at a power density of 5 kW kg− 1, highlighting its significant potential for practical applications.

Co2+-coordination-assisted enhancement of mechanical and iodynamic properties of 3D graphene-based double network hydrogels for all-solid-state supercapacitors
    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials
        2.2 Synthesized methods
            2.2.1 Synthesis of graphene oxide
            2.2.2 Synthesis of three-dimensional N-doped graphene
            2.2.3 Synthesis of 3DNG-Co2+P(AA-co-DMA) DN hydrogel
        2.3 Fabrication of all-solid-state supercapacitors
    3 Results and discussion
    4 Conclusions
    Acknowledgements 
    References

• Binhong He(Key Laboratory of Hunan Province for Advanced Carbon‑Based Functional Materials, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China)
• Shuntao Wen(Key Laboratory of Hunan Province for Advanced Carbon‑Based Functional Materials, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China)
• Zhiming Wen(Key Laboratory of Hunan Province for Advanced Carbon‑Based Functional Materials, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China)
• Yan Liang(Key Laboratory of Hunan Province for Advanced Carbon‑Based Functional Materials, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China)
• Qianxi Yang(Key Laboratory of Hunan Province for Advanced Carbon‑Based Functional Materials, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China)
• Minjie Zhou(Key Laboratory of Hunan Province for Advanced Carbon‑Based Functional Materials, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China)
• Wei Wang(Key Laboratory of Hunan Province for Advanced Carbon‑Based Functional Materials, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China) Corresponding author
• Guo‑Xiang Wang(Key Laboratory of Hunan Province for Advanced Carbon‑Based Functional Materials, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China, School of Chemistry and Chemical Engineering, Hunan Institute of Science and Technology, Yueyang 414006, Hunan Province, People’s Republic of China)